找了半天，总算找到个比较全面点的，存一下

const
py: array[216..247] of string = (
{216}'CJWGNSPGCGNESYPB' + 'TYYZDXYKYGTDJNMJ' + 'QMBSGZSCYJSYYZPG' +
{216}'KBZGYCYWYKGKLJSW' + 'KPJQHYZWDDZLSGMR' + 'YPYWWCCKZNKYDG',
{217}'TTNJJEYKKZYTCJNM' + 'CYLQLYPYQFQRPZSL' + 'WBTGKJFYXJWZLTBN' +
{217}'CXJJJJZXDTTSQZYC' + 'DXXHGCKBPHFFSSYY' + 'BGMXLPBYLLLHLX',
{218}'SPZMYJHSOJNGHDZQ' + 'YKLGJHXGQZHXQGKE' + 'ZZWYSCSCJXYEYXAD' +
{218}'ZPMDSSMZJZQJYZCD' + 'JEWQJBDZBXGZNZCP' + 'WHKXHQKMWFBPBY',
{219}'DTJZZKQHYLYGXFPT' + 'YJYYZPSZLFCHMQSH' + 'GMXXSXJJSDCSBBQB' +
{219}'EFSJYHXWGZKPYLQB' + 'GLDLCCTNMAYDDKSS' + 'NGYCSGXLYZAYBN',
{220}'PTSDKDYLHGYMYLCX' + 'PYCJNDQJWXQXFYYF' + 'JLEJBZRXCCQWQQSB' +
{220}'ZKYMGPLBMJRQCFLN' + 'YMYQMSQYRBCJTHZT' + 'QFRXQHXMJJCJLX',
{221}'QGJMSHZKBSWYEMYL' + 'TXFSYDSGLYCJQXSJ' + 'NQBSCTYHBFTDCYZD' +
{221}'JWYGHQFRXWCKQKXE' + 'BPTLPXJZSRMEBWHJ' + 'LBJSLYYSMDXLCL',
{222}'QKXLHXJRZJMFQHXH' + 'WYWSBHTRXXGLHQHF' + 'NMCYKLDYXZPWLGGS' +
{222}'MTCFPAJJZYLJTYAN' + 'JGBJPLQGDZYQYAXB' + 'KYSECJSZNSLYZH',
{223}'ZXLZCGHPXZHZNYTD' + 'SBCJKDLZAYFMYDLE' + 'BBGQYZKXGLDNDNYS' +
{223}'KJSHDLYXBCGHXYPK' + 'DQMMZNGMMCLGWZSZ' + 'XZJFZNMLZZTHCS',
{224}'YDBDLLSCDDNLKJYK' + 'JSYCJLKOHQASDKNH' + 'CSGANHDAASHTCPLC' +
{224}'PQYBSDMPJLPCJOQL' + 'CDHJJYSPRCHNKNNL' + 'HLYYQYHWZPTCZG',
{225}'WWMZFFJQQQQYXACL' + 'BHKDJXDGMMYDJXZL' + 'LSYGXGKJRYWZWYCL' +
{225}'ZMSSJZLDBYDCPCXY' + 'HLXCHYZJQSQQAGMN' + 'YXPFRKSSBJLYXY',
{226}'SYGLNSCMHCWWMNZJ' + 'JLXXHCHSYD CTXRY' + 'CYXBYHCSMXJSZNPW' +
{226}'GPXXTAYBGAJCXLYS' + 'DCCWZOCWKCCSBNHC' + 'PDYZNFCYYTYCKX',
{227}'KYBSQKKYTQQXFCWC' + 'HCYKELZQBSQYJQCC' + 'LMTHSYWHMKTLKJLY' +
{227}'CXWHEQQHTQHZPQSQ' + 'SCFYMMDMGBWHWLGS' + 'LLYSDLMLXPTHMJ',
{228}'HWLJZYHZJXHTXJLH' + 'XRSWLWZJCBXMHZQX' + 'SDZPMGFCSGLSXYMJ' +
{228}'SHXPJXWMYQKSMYPL' + 'RTHBXFTPMHYXLCHL' + 'HLZYLXGSSSSTCL',
{229}'SLDCLRPBHZHXYYFH' + 'BBGDMYCNQQWLQHJJ' + 'ZYWJZYEJJDHPBLQX' +
{229}'TQKWHLCHQXAGTLXL' + 'JXMSLXHTZKZJECXJ' + 'CJNMFBYCSFYWYB',
{230}'JZGNYSDZSQYRSLJP' + 'CLPWXSDWEJBJCBCN' + 'AYTWGMPABCLYQPCL' +
{230}'ZXSBNMSGGFNZJJBZ' + 'SFZYNDXHPLQKZCZW' + 'ALSBCCJXJYZHWK',
{231}'YPSGXFZFCDKHJGXD' + 'LQFSGDSLQWZKXTMH' + 'SBGZMJZRGLYJBPML' +
{231}'MSXLZJQQHZSJCZYD' + 'JWBMJKLDDPMJEGXY' + 'HYLXHLQYQHKYCW',
{232}'CJMYYXNATJHYCCXZ' + 'PCQLBZWWYTWBQCML' + 'PMYRJCCCXFPZNZZL' +
{232}'JPLXXYZTZLGDLDCK' + 'LYRLZGQTGJHHGJLJ' + 'AXFGFJZSLCFDQZ',
{233}'LCLGJDJCSNCLLJPJ' + 'QDCCLCJXMYZFTSXG' + 'CGSBRZXJQQCTZHGY' +
{233}'QTJQQLZXJYLYLBCY' + 'AMCSTYLPDJBYREGK' + 'JZYZHLYSZQLZNW',
{234}'CZCLLWJQJJJKDGJZ' + 'OLBBZPPGLGHTGZXY' + 'GHZMYCNQSYCYHBHG' +
{234}'XKAMTXYXNBSKYZZG' + 'JZLQJDFCJXDYGJQJ' + 'JPMGWGJJJPKQSB',
{235}'GBMMCJSSCLPQPDXC' + 'DYYKYWCJDDYYGYWR' + 'HJRTGZNYQLDKLJSZ' +
{235}'ZGZQZJGDYKSHPZMT' + 'LCPWNJAFYZDJCNMW' + 'ESCYGLBTZCGMSS',
{236}'LLYXQSXSBSJSBBGG' + 'GHFJLYPMZJNLYYWD' + 'QSHZXTYYWHMCYHYW' +
{236}'DBXBTLMSYYYFSXJC' + 'SDXXLHJHF SXZQHF' + 'ZMZCZTQCXZXRTT',
{237}'DJHNNYZQQMNQDMMG' + 'LYDXMJGDHCDYZBFF' + 'ALLZTDLTFXMXQZDN' +
{237}'GWQDBDCZJDXBZGSQ' + 'QDDJCMBKZFFXMKDM' + 'DSYYSZCMLJDSYN',
{238}'SPRSKMKMPCKLGDBQ' + 'TFZSWTFGGLYPLLJZ' + 'HGJJGYPZLTCSMCNB' +
{238}'TJBQFKTHBYZGKPBB' + 'YMTDSSXTBNPDKLEY' + 'CJNYCDYKZDDHQH',
{239}'SDZSCTARLLTKZLGE' + 'CLLKJLQJAQNBDKKG' + 'HPJTZQKSECSHALQF' +
{239}'MMGJNLYJBBTMLYZX' + 'DCJPLDLPCQDHZYCB' + 'ZSCZBZMSLJFLKR',
{240}'ZJSNFRGJHXPDHYJY' + 'BZGDLJCSEZGXLBLH' + 'YXTWMABCHECMWYJY' +
{240}'ZLLJJYHLGBDJLSLY' + 'GKDZPZXJYYZLWCXS' + 'ZFGWYYDLYHCLJS',
{241}'CMBJHBLYZLYCBLYD' + 'PDQYSXQZBYTDKYYJ' + 'YYCNRJMPDJGKLCLJ' +
{241}'BCTBJDDBBLBLCZQR' + 'PPXJCGLZCSHLTOLJ' + 'NMDDDLNGKAQHQH',
{242}'JHYKHEZNMSHRP QQ' + 'JCHGMFPRXHJGDYCH' + 'GHLYRZQLCYQJNZSQ' +
{242}'TKQJYMSZSWLCFQQQ' + 'XYFGGYPTQWLMCRNF' + 'KKFSYYLQBMQAMM',
{243}'MYXCTPSHCPTXXZZS' + 'MPHPSHMCLMLDQFYQ' + 'XSZYJDJJZZHQPDSZ' +
{243}'GLSTJBCKBXYQZJSG' + 'PSXQZQZRQTBDKYXZ' + 'KHHGFLBCSMDLDG',
{244}'DZDBLZYYCXNNCSYB' + 'ZBFGLZZXSWMSCCMQ' + 'NJQSBDQSJTXXMBLT' +
{244}'XZCLZSHZCXRQJGJY' + 'LXZFJPHYXZQQYDFQ' + 'JJLZZNZJCDGZYG',
{245}'CTXMZYSCTLKPHTXH' + 'TLBJXJLXSCDQXCBB' + 'TJFQZFSLTJBTKQBX' +
{245}'XJJLJCHCZDBZJDCZ' + 'JDCPRNPQCJPFCZLC' + 'LZXBDMXMPHJSGZ',
{246}'GSZZQLYLWTJPFSYA' + 'SMCJBTZYYCWMYTCS' + 'JJLQCQLWZMALBXYF' +
{246}'BPNLSFHTGJWEJJXX' + 'GLLJSTGSHJQLZFKC' + 'GNNDSZFDEQFHBS',
{247}'AQTGYLBXMMYGSZLD' + 'YDQMJJRGBJTKGDHG' + 'KBLQKBDMBYLXWCXY' +
{247}'TTYBKMRTJZXQJBHL' + 'MHMJJZMQASLDCYXY' + 'QDLQCAFYWYXQHZ'
);

function ChnPy(Value: array of char): Char;
begin
Result := #0;
case Byte(Value[0]) of
176:
case Byte(Value[1]) of
161..196: Result := 'A';
197..254: Result := 'B';
end; {case}
177:
Result := 'B';
178:
case Byte(Value[1]) of
161..192: Result := 'B';
193..205: Result := 'C';
206: Result := 'S'; //参
207..254: Result := 'C';
end; {case}
179:
Result := 'C';
180:
case Byte(Value[1]) of
161..237: Result := 'C';
238..254: Result := 'D';
end; {case}
181:
Result := 'D';
182:
case Byte(Value[1]) of
161..233: Result := 'D';
234..254: Result := 'E';
end; {case}
183:
case Byte(Value[1]) of
161: Result := 'E';
162..254: Result := 'F';
end; {case}
184:
case Byte(Value[1]) of
161..192: Result := 'F';
193..254: Result := 'G';
end; {case}
185:
case Byte(Value[1]) of
161..253: Result := 'G';
254: Result := 'H';
end; {case}
186:
Result := 'H';
187:
case Byte(Value[1]) of
161..246: Result := 'H';
247..254: Result := 'J';
end; {case}
188..190:
Result := 'J';
191:
case Byte(Value[1]) of
161..165: Result := 'J';
166..254: Result := 'K';
end; {case}
192:
case Byte(Value[1]) of
161..171: Result := 'K';
172..254: Result := 'L';
end; {case}
193:
Result := 'L';
194:
case Byte(Value[1]) of
161..231: Result := 'L';
232..254: Result := 'M';
end; {case}
195:
Result := 'M';
196:
case Byte(Value[1]) of
161..194: Result := 'M';
195..254: Result := 'N';
end; {case}
197:
case Byte(Value[1]) of
161..181: Result := 'N';
182..189: Result := 'O';
190..254: Result := 'P';
end; {case}
198:
case Byte(Value[1]) of
161..217: Result := 'P';
218..254: Result := 'Q';
end; {case}
199:
Result := 'Q';
200:
case Byte(Value[1]) of
161..186: Result := 'Q';
187..245: Result := 'R';
246..254: Result := 'S';
end; {case}
201..202:
Result := 'S';
203:
case Byte(Value[1]) of
161..249: Result := 'S';
250..254: Result := 'T';
end; {case}
204:
Result := 'T';
205:
case Byte(Value[1]) of
161..217: Result := 'T';
218..254: Result := 'W';
end; {case}
206:
case Byte(Value[1]) of
161..243: Result := 'W';
244..254: Result := 'X';
end; {case}
207..208:
Result := 'X';
209:
case Byte(Value[1]) of
161..184: Result := 'X';
185..254: Result := 'Y';
end; {case}
210..211:
Result := 'Y';
212:
case Byte(Value[1]) of
161..208: Result := 'Y';
209..254: Result := 'Z';
end; {case}
213..215:
Result := 'Z';
216..247:
Result := py[Byte(Value[0])][Byte(Value[1]) - 160];
end; {case}
end;

function ChnToPY(Value: string): string;
var
I, L: Integer;
C: array[0..1] of char;
R: Char;
begin
Result := '';
L := Length(Value);
I := 1;
while I <= (L - 1) do
begin
if Value[I] < #160 then
begin
Result := Result + Value[I];
Inc(I);
end
else
begin
C[0] := Value[I];
C[1] := Value[I + 1];
R := ChnPY(C);
if r <> #0 then
Result := Result + R;
Inc(I, 2);
end;
end;
if I = L then
Result := Result + Value[L];
end;



上面这个处理范围比较广，对于双单字，较偏的字也都能处理。


网上还流行的一段代码：


////////////////////////////////////////////////////////////////////////////
// 函数: GetPYIndexChar(strChinese: string;bUpCase: Boolean = True): char;
//
// 函数功能:获取汉字的拼音首字符.
// 例: GetPYIndexChar('程') 将返回'C'.
//
// 注意:对于多于一个汉字的输入(string类型)只有第一个有效,但不会产生错误
// 例如,GetPYIndexChar('程序')也将返回'C'.
//
// 第二个参数决定返回大写还是小写 , 缺省为大写 .
////////////////////////////////////////////////////////////////////////////
function GetPYIndexChar(strChinese: string;bUpCase: Boolean = True): char;
begin
// 根据汉字表中拼音首字符分别为"A"至"Z"的汉字内码范围，
// 要检索的汉字只需要检查它的内码位于哪一个首字符的范围内，
// 就可以判断出它的拼音首字符。
case WORD(strChinese[1]) shl 8 + WORD(strChinese[2]) of
$B0A1..$B0C4 : result := 'A';
$B0C5..$B2C0 : result := 'B';
$B2C1..$B4ED : result := 'C';
$B4EE..$B6E9 : result := 'D';
$B6EA..$B7A1 : result := 'E';
$B7A2..$B8C0 : result := 'F';
$B8C1..$B9FD : result := 'G';
$B9FE..$BBF6 : result := 'H';
$BBF7..$BFA5 : result := 'J';
$BFA6..$C0AB : result := 'K';
$C0AC..$C2E7 : result := 'L';
$C2E8..$C4C2 : result := 'M';
$C4C3..$C5B5 : result := 'N';
$C5B6..$C5BD : result := 'O';
$C5BE..$C6D9 : result := 'P';
$C6DA..$C8BA : result := 'Q';
$C8BB..$C8F5 : result := 'R';
$C8F6..$CBF9 : result := 'S';
$CBFA..$CDD9 : result := 'T';
$CDDA..$CEF3 : result := 'W';
$CEF4..$D188 : result := 'X';
$D1B9..$D4D0 : result := 'Y';
$D4D1..$D7F9 : result := 'Z';
else
result := char(0);
end;
if not bUpCase then
begin // 转换为小写
result := Chr(Ord(result)+32);
end;
end;

////////////////////////////////////////////////////////////////////////////
// 函数: GetPYIndexStr(strChinese: string;bUpCase: Boolean = True): string;
//
// 函数功能:获取多个汉字的拼音首字符组成的字符串.
// 例: GetPYIndexStr('程') 将返回'C'.
// GetPYIndexStr('程序')将返回'CX'.
//
// 第二个参数决定返回大写还是小写 , 缺省为大写 .
////////////////////////////////////////////////////////////////////////////
function GetPYIndexStr(strChinese: string;bUpCase: Boolean = True): string;
var
strChineseTemp : string;
cTemp : Char;
begin
result := '';
strChineseTemp := strChinese;
while strChineseTemp<>'' do
begin
cTemp := GetPYIndexChar(strChineseTemp);
if not bUpCase then
begin // 转换为小写
cTemp := Chr(Ord(cTemp)+32);
end;
result := result + string(cTemp);
strChineseTemp := Copy(strChineseTemp,3,Length(strChineseTemp));
end;
end;

处理汉字的范围有限，比如深圳的“圳”，“抻”等字都无法处理