SHGetSpecialFolderLocation

uses shlobj;

function GetDesktopFolder():string;
var
  pItem: PItemIDList;
  temp: array[0..MAX_PATH] of Char;
begin
  SHGetSpecialFolderLocation(0, CSIDL_DESKTOP, pItem); //CSIDL_DESKTOP：桌面；
  FillChar(temp, MAX_PATH, #0);
  SHGetPathFromIDList(pItem, PChar(@temp));
  Result :=PChar(@temp);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Caption:=getDesktopFOlder;
end;