Code:

function GetRTFText(ARichEdit: TRichedit): string;

var

  ss: TStringStream;

  emptystr: string;

begin

  emptystr := '';

  ss := TStringStream.Create(emptystr);

  try

    ARichEdit.PlainText := False;

    ARichEdit.Lines.SaveToStream(ss);

    Result := ss.DataString;

  finally

    ss.Free

  end;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

  Memo1.Text := GetRTFText(RichEdit1);

end;