Many studies have examined that bullying bystander intervention refers to a positive, pro-social bystander behavior that prevents the sustained development of bullying incidents in the face of school bullying. Limited research has investigated the different roles of bystanders and the factors that influence their behavior. This study attempts to explore the association between being bullied and intervention by bystanders in adolescent school bullying, the role of moral disengagement, and the status of only children in this context. For this purpose, 2113 middle school students completed the Being Bullied Behavior Scale, Bystander Intervention Scale, and Moral Disengagement Scale. The study findings indicate that (1) being bullied positively anticipates the intervention by bystanders in school bullying; (2) further, moral disengagement plays an essential role in mediating the effects of bullying on bystander intervention, and being bullied "masks" the related positive influence on the bystander intervention through the negative mediation of moral disengagement; and (3) finally, the status of being an only child moderates the first half of this mediating effect. Based on this, this study implies that being bullied is more effective at predicting moral disengagement for only children. Consequently, the influence of being bullied on bystander intervention in school bullying is revealed in this study, which exhibits significant practical implications for improving the ecological environment of school bullying.

许多研究考察，欺凌旁观者干预是指面对校园欺凌，旁观者采取积极的、亲社会的行为，阻止欺凌事件的持续发展。有限的研究调查了旁观者的不同角色以及影响他们行为的因素。本研究试图探讨青少年校园欺凌中被欺凌与旁观者干预之间的关联、道德脱离的作用以及在此背景下独生子女的地位。为此，2113名中学生完成了被欺凌行为量表、旁观者干预量表和道德脱离量表。研究结果表明：（1）被欺负会积极预期旁观者对校园欺凌的干预；（2）进一步，道德脱离在中介欺凌对旁观者干预的影响中发挥着重要作用，而被欺负通过道德脱离的负向中介“掩盖”了相关的对旁观者干预的积极影响；(3)最后，独生子女的身份调节了这一中介效应的前半部分。基于此，这项研究表明，被欺凌可以更有效地预测独生子女的道德脱离。因此，本研究揭示了被欺凌对旁观者干预校园欺凌行为的影响，对于改善校园欺凌生态环境具有重要的现实意义。