自己解答:
rs:=self.adocUser.Execute('select * from a');
 rs.MoveFirst;
 while not rs.Eof do
 begin
   for i:=0 to rs.Fields.Count -1 do
   begin
   ExcelWorksheet.Cells.Item[rs.AbsolutePosition,i+1].value:=rs.Fields[i].Value;
   end;
   rs.MoveNext;
 end;