Objective To explore the mechanisms of negative life events on non-suicidal self-injury （NSSI） behavior in adolescents. Methods A total of 1 800 adolescents from the first year of junior high school to second year of senior high school in several cities in Heilongjiang Province were selected as the research subjects from January 2021 to January 2022. Adolescent Non-Suicidal Self-Injury Questionnaire and Adolescent Self-rating Life Events Checklist were applied in the investigation. Spearman correlation analysis was used to investigate the correlation between NSSI behavior， NSSI motivation， emotion regulation， self reinforcement， interpersonal influence， and negative life events in adolescents. Process models 4 and 5 in SPSS 25.0 were used for mediation effect analysis. Results A total of 1 666 valid questionnaires were ultimately collected， with an effective response rate of 92.6%. The overall detection rate of NSSI behavior among adolescents was 25.0% （416/ 1 666）. Negative life events in adolescents were positively correlated with NSSI motivation and NSSI behavior， and NSSI behavior was positively correlated with NSSI motivation（r=0.32、0.26、0.22，all P ＜ 0.01）. The mediation model analysis showed that the three types of NSSI motivations （emotion regulation， self reinforcement， and interpersonal influence） had a mediating effect between negative life events and NSSI behavior， with an effect value of 0.012， accounting for 26.67% of the total effect value. The moderation effect analysis found that gender could regulate the direct effect of negative life events on NSSI behavior， that is， compared to the male population， negative life events had a stronger positive predictive effect on NSSI behavior in female adolescents. Conclusions It is crucial to acknowledge the role of adverse life events and the mediating function of NSSI motivation in adolescent NSSI behaviors， particularly among female adolescents， to formulate effective prevention strategies.