Abstract: Objective To understand the status of mental health of medical students,compare the effect of PBL teaching method and traditional teaching method in improving the mental health of medical students,and to provide a basis for the effective teaching strategies in mental health education. Methods Via the convenient cluster sampling method and the SCL-90 scale to investigate the students in a medical school,357 valid samples were obtained and randomly divided into the control group (n=178) and experimental group (n=179),who received 16 weeks of teaching experiment.The independent sample t-test and chi-square test were used for intergroup comparison. Results The total score of SCL-90 was 129.44,with a 15.97% positive rate,and the average score of all the factors were between 1.21 and 1.81,which were lower than the national norm level.After the experiment,the total score of the control group decreased by 4.93%,the positive rate decreased by 2.99%,and the average score of all the factors reduced between 0.04 and 0.09 scores,among which somatization,interpersonal sensitivity,anxiety and hostility factors has statistical significance (P<0.05).The total score of the experimental group decreased by 6.31%,and the positive rate decreased by 7.51%,with a significant difference (P<0.05) and except for depression,the average score of all factors reduced between 0.06 and 0.11 scores,with a significant difference (P<0.05). Conclusion Compared with that of the national college students'norm,the mental health of medical students is better.Both the traditional teaching method and PBL teaching method can reduce the self-evaluation score of psychological symptoms,but the latter can have a better effect.