Objective: To explore the relationships among perceived stress, emotion regulation strategies, and abnormal eating behavior among medical students, in order to provide healthy eating behavior reference for medical students, especially under pressure. Methods: Chinese Perceived Stress Questionnaire, Emotion Regulation Questionnaire, and Dutch Eating Behavior Questionnaire were administered among 777 students from three medical universities in Shanxi seleceted by a stratified random cluster sampling method. Results: There were significant differences in unhealthy eating behavior by gender and major. Abnormal eating problem score of clinical medicine students was significantly higher than that of non-clinical medicine students (t=3.56,P<0.01); Scores of restrained eating behavior, emotional eating behavior, and exogenic eating behavior of clinical medicine students were all significantly higher than those of non-clinical medicine students (t=3.45, 3.04, 4.19, P<0.01). Abnormal eating behavior, and restrained eating behavior and exogenic eating behavior in female students were significantly higher than those of male students (t=2.28, 2.58, 2.46, P<0.05). The perceived stress significantly and positively correlated with the abnormal eating behavior (P<0.01); Cognitive reappraisal and expressive inhibition significantly and negatively correlated with abnormal eating behavior respectively (P<0.01); No significant association was found between expressive inhibition and abnormal eating behavior. Cognitive reappraisal mediated the association between abnormal eating behavior with perceived stress which accounted for 36.89%, mediating effect in boys was higher than that of girls. However, expressive inhibition showed no similar effect and gender difference. Conclusion Perceived stress can influence abnormal eating behavior of medical students through cognitive reappraisal directly or indirectly, while expressive inhibition shows no such mediating effect. For medical students under pressure, the skill of emotion regulation through cognitive reappraisal, emotion expression as well as appropriate coping style under pressure should be developed.