uses WinSock; 

function LocalIP: String; 
 type TaPInAddr = Array[0..10] of PInAddr; 
       PaPInAddr = ^TaPInAddr; 
var phe: PHostEnt;
    pptr: PaPInAddr;
    Buffer: Array[0..63] of AnsiChar; 
    i: Integer;
    GInitData: TWSAData; 
begin
  WSAStartup($101, GInitData); 
  Result := ''; 
  GetHostName(Buffer, SizeOf(Buffer)); 
  phe := GetHostByName(buffer); 
  if phe = nil then 
    Exit; 
  pPtr := PaPInAddr(phe^.h_addr_list); 
  i := 0; 
  while pPtr^[i] <> nil do 
   begin 
     Result := inet_ntoa(pptr^[i]^); 
     Inc(i); 
   end; WSACleanup; 
  end; 
//测试:
procedure TForm1.Button1Click(Sender: TObject); 
begin 
ShowMessage(LocalIP); // 
end;