Objective:To investigate the occurrence and characteristics of post-traumatic stress disorder (PTSD) in medical school undergraduates, in order to provide reference to promote their mental health.Methods:Adopting stratified and cluster sampling method, 883 undergraduates from Xi ′an Medical College were selected and surveyed on March 9-16, 2020 by general condition questionnaire, PTSD Checklist-Civilian Version (PCL-C) and Simplified Coping Style Questionnaire (SCSQ). Results:The total score of PCL-C was (24.34 ± 8.12) points, (7.19 ± 2.61) points for re-experiencing symptoms, (9.87 ± 3.49) points for avoidance symptoms, and (7.28 ± 2.85) points for arousal symptoms. The incidence of PTSD was 8.2% (72/883). The scores of PTSD symptoms were higher in grade four students and whose coping tendency was negative, (26.37 ± 9.26) and (26.49 ± 9.48), respectively ( F value was 3.065, P<0.05; t value was -9.357, P<0.001). Positive coping scores were negatively correlated to PTSD symptoms ( r value was -0.130, P<0.001), while negative coping scores were positively correlated to PTSD ( r value was 0.244, P<0.001). Medical students with strong professional attitude had lower PTSD scores (23.23 ± 6.92)( F value was 21.650, P<0.001) and lower negative coping scores (8.21 ± 4.65) ( F value was 6.567, P<0.001). Conclusions:The incidence of PTSD was 8.2% in medical school undergraduates, whose severity was related to grade and coping tendency. Appropriate crisis intervention should be taken among medical students to improve their positive coping style, strengthen their professional identification and promote their mental health.