Abstract: Objective: Based on social information processing theory, a moderated-mediation model was constructed according to the dual attributes of weight self-stigma(WSS), so as to explore the double-edged sword effect and boundary conditions of weight selfstigma on adolescents' physical exercise(PE). Methods: A package of surveys, including the weight self-stigma questionnaire,relatives' physical activity encouragement questionnaire, exercise value cognition questionnaire, negative physical activity affect scale and physical activity rating scale-3, were used to survey 3 406 adolescents. Results: 1) The WSS indirectly affected adolescents' PE through EVC, NEE, and the chain-mediated effect of both EVC and NEE; 2) relatives' physical activity encouragement(RPAE)positively moderated the mediating effect of EVC between WSS and adolescents' PE, namely, the higher level of RPAE, the stronger the mediating effect, and vice versa; 3) RPAE negatively moderated the mediating effect of NEE between WSS and adolescents' PE,namely, the higher level of RPAE, the weaker the mediating effect, and vice versa; 4) RPAE positively moderated the chain mediation effect of EVC between WSS and adolescents' PE, namely, the higher level of RPAE, the stronger the chain mediation effect, and vice versa. Conclusions: WSS significantly promoted the EVC and weaken the NEE, which drove the adolescents to improve PE, and the RPAE played a double-edged sword effect in the above process. In order to effectively cope with the doubleedged sword effects of WSS, it is recommended to skillfully use WSS to enhance the positive effect of adolescents' PE, while preventing its negative effect.