Objective: To explore an effective evaluation method for students’ self- and peer-assessment. Methods: The students of 6 groups participated in extracurricular teaching activities were selected as research subject. Traditional method (final score = mean score of group/2 + teacher’s score/2) and mean difference method [final score = teacher’s score-(mean difference of group - mean difference of all groups)] were used to calculate final score of each group

and effect of two methods are compared. Results: Scores of most groups were higher than the teacher's scores

and high scores were given by group 3 in self- and peer-assessment. The final score of all groups were higher than teacher's scores in traditional method. Compared with teacher's scores

final scores increased significantly in group 1

4

5 below mean difference

final score decreased significantly in group 2

3 above mean difference

and final score did not differ in group 6 equal to mean difference in mean difference method. Conclusion: The mean difference method can reflect the effect of student's elf- and peer-assessment

and guide student to make objective and accurate evaluation. It is a more reasonable and scientific evaluation method for self- and peer-assessment.