School bullying and loneliness have become common problems in adolescent interpersonal relationships. The increase of school bullying in recent years is closely related to adolescents’ loneliness, and loneliness may also affect the implementation of school bullying. Meanwhile, childhood emotional maltreatment plays an important role in interpersonal relationship problems triggered by adolescence, which has attracted a lot of attention from researchers. The purpose of this study was to explore the mutual and transactional relationship between loneliness and school bullying under childhood emotional maltreatment. A total of 1214 Chinese high school students (Mage = 15.46, SD = 0.71) completed the measures of childhood emotional maltreatment, loneliness, and school bullying. They provided data in three waves (T1, T2, and T3, 6 months apart). The results reality that loneliness under childhood emotional abuse and school bullying are correlated and that childhood emotional abuse significantly predicts loneliness and school bullying in adolescence. Specifically, loneliness positively predicted school bullying, but the predictive effect of school bullying on loneliness was influenced by gender. Moreover, childhood emotional maltreatment can lead to the perpetration of school bullying by triggering loneliness in adolescents. The results of the study, although unexpected, also reveal social problems and provide new ideas for studying adolescent interpersonal problems.