Objective: To evaluate the effectiveness of professional competency training on the psychological commissioners in college,and to provide a reference for promoting mental health education in colleges. Methods: Using the purposive sampling method, 198 psychological commissioners and 210 nonpsychological commissioners from freshmen in a university in Nanjing were selected for questionnaire survey. SPSS 21.0 statistic software was utilized for data analysis. Results: The levels of knowledge and skills of mental health practice among trained psychological commissioners showed no difference with those nonpsychological commissioner students before training(t=0.34, -0.08, P>0.05). Compared with pretraining, the paired sample ttest indicated that knowledge, practical skills, and expected skills among qualified psychological commissioners increased significantly after training, respectively(t=23.34, 23.21, 3.30, P<0.01). Understanding of job duty, basic helping skills, interpersonal communication, mental problems among college students, classroombased psychological activities, psychological counseling, mental disorders identification, group counseling and crisis intervention increased significantly after training(P<0.01). Conclusion The professional competency training could substantially improve mental health practice, skills, as well as attitudes among psychological commissioners recruited from college freshmen.