你需要的是这样的函数吧？

function AnsiToUnicode(Ansi: string):string;

var

 s:string;

 i:integer;

 j,k:string[2];

 a:array [1..1000] of char;

begin

 s:='';

 StringToWideChar(Ansi,@(a[1]),500);

 i:=1;

 while ((a[i]<>#0) or (a[i+1]<>#0)) do begin

  j:=IntToHex(Integer(a[i]),2);

  k:=IntToHex(Integer(a[i+1]),2);

  s:=s+k+j;

  i:=i+2;

 end;

  Result:=s;

end;

附上反编码的函数

function ReadHex(AString:string):integer;

begin

 Result:=StrToInt('$'+AString)

end;

function UnicodeToAnsi(Unicode: string):string;

var

 s:string;

 i:integer;

 j,k:string[2];

begin

 i:=1;

 s:='';

 while i<Length(Unicode)+1 do begin

  j:=Copy(Unicode,i+2,2);

  k:=Copy(Unicode,i,2);

  i:=i+4;

  s:=s+Char(ReadHex(j))+Char(ReadHex(k));

 end;

 if s<>'' then

  s:=WideCharToString(PWideChar(s+#0#0#0#0))

 else

  s:='';

 Result:=s;

end;

根据你的需要进行改动就可以了。