<p>Parent-child conflict tends to be more frequent and intense during adolescence. Given the unique developmental characteristics of adolescence and the negative impacts of parent-child conflict, exploring the influencing factors and mechanisms of parent-child conflict has become an urgent issue. Based on family systems theory, this study aims to investigate the associations between interparental conflict and parent-child conflict, the mediating role of psychological reactance, as well as the gender differences in these mediating effects. Using a longitudinal design, a total of 764 adolescents completed data collection at three time points. After controlling for autoregressive effects, the results showed that T1 interparental conflict frequency significantly positively predicted T3 mother-child conflict frequency and intensity. In addition, T1 interparental conflict intensity significantly positively predicted T3 father-child conflict frequency and intensity, as well as T3 mother-child conflict frequency. Further mediation analysis revealed that psychological reactance played a significant mediating role in the associations between interparental conflict intensity and parent-child conflict. Additionally, gender differences were observed in the mediating role of psychological reactance. The current findings contribute to a deeper understanding of parent-child conflict from the perspective of interparental conflict, providing practical insights for improving family relationships and adolescent development.</p>