Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

 procedure TForm1.Button1Click(Sender: TObject);
 var
   i, k: Integer;
 begin
   with StringGrid1 do
     for i := 0 to ColCount - 1 do
       for k := 0 to RowCount - 1 do
         Cells[i, k] := '';
 end;