You can easily show user id numbers for assignments and other graded activities in the grader report in Moodle 1.9 by setting 'Show user id number' to Yes in the grader report preferences. Please see Grader report preferences for more details.
Thanks a lot Helen. Maybe I have mis-conveyed what I would like to do.
If we are going to view the report of grades from all courses, it is possible to do the way you kindly pointed out. ?But if we just want to view the submission of certain course, then there is no choice at all but the default report.
Anyway, I have figured out how to do that by modifying a bit in mod/assignment/lib.php. I have attached here so that you may consider updating in the next relealse.