Objective To explore the relationships between inappropriate parenting styles,emotional regulation strategies and self-injury.Methods A total of 1 096 medical students anonymously completed adolescents self-harm scale,emotion regulation scale (ERS) and the rejection and over-protection subscales of parental bonding instrument (PBI).Results The scores of paternal rejection,maternal rejection,paternal over-protection,maternal over-protection,cognitive reappraisal,expression suppression and self-injury were (4.3±3.3),(3.9±3.0),(5.7±3.3),(6.1±3.5),(36.1±6.7),(25.7±7.4) and (1.0±2.9),respectively.The scores of self-injury were positively correlated with the scores of paternal rejection,maternal rejection,paternal over-protection,maternal over-protection and expression suppression (r =0.08-0.20,P＜ 0.01),meanwhile negatively correlated with the scores of cognitive reappraisal(r=-0.10,P＜0.01).Cognitive reappraisal mediated the relationship between parental rejection and self-injury,which accounted for 9.3％.Expression suppression mediated the relationship between parental rejection,parental over-protection and self-injury,which accounted for 14.5％ and 17.9％,respectively.Conclusion The emotion regulation strategy act as a mediator between the inappropriate parental styles and self-injury in medical students.In addition,different emotion regulation strategies (cognitive reappraisal and expression suppression) play different roles in such relationship.