Objective: To study the relationship between emotional contagion, professional behavior, and moral judgment of student teachers and the mediating role of moral judgment among them. Methods: The "Emotional Contagion Questionnaire", "Pro-social Tendencies Measure for Adolescent (PTM)" and "Moral Judgment Test (MJT)" was used to survey 448 student teachers. Results: The emotional contagion and pro-social behavior of student teachers have no significant differences between gender and urban and rural areas, but significant differences in professional nature. No significant differences were observed in moral judgment between urban and rural areas and major character, but significant in gender. A significant positive correlation was detected between emotional contagion and pro-social behavior. Conclusion: Moral judgment plays a partially mediating role in the relationship between emotional contagion and pro-social behavior.