with DataModule1.ADOQuery2 do
      begin
        close;
        sql.Clear;
        sql.Add('select * from operator where user=:user');
        parameters.ParamByName('user').Value :=edit1.text;
        open;
        if (FieldValues['password']=edit1.Text) and (FieldValues['user']=username)  then
            begin
                if edit2.Text=edit3.Text then
                  begin
                    close;
                    sql.Clear;
                    sql.text:='update operator set password=:u '+'where password='''+edit1.text+'''';
                    parameters.ParamByName('u').Value :=edit2.text;
                    ExecSQL;
                    showmessage('密码修改成功');
                  end
                else
                  showmessage('新密码不相等');
              end
        else
          showmessage('原密码错误');
      end;

看下错误信息是什么呢

说update语法错误

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哈哈，应该是 where 前要加一个空格。