This study is a first-of-its-kind three-wave longitudinal study of the causal relationship between victimization and reactive aggression. This study addresses three gaps of prior research. First, this study is longitudinal, whereas most prior studies have been cross-sectional. Second, most studies on child victimization and aggression have been conducted in the West, even though there is evidence that peer aggression is common and very serious in China as well. Third, scholars usually lump all victims together without considering their different subtypes. However, victims can be classified as either aggressive or pure victims based on aggressiveness. This study is also the first to explore the underlying mediating and moderating mechanisms in aggressive and pure victims and to examine developmental pathways from victimization to reactive aggression for different subtypes of victims by comparing emotional states (depression), emotional regulation skills, cognitive style (causal attribution), and behavioral changes (hyperactivity) based on the social information processing (SIP) model. In contrast to prior studies with small samples, this study uses the largest sample of aggressive and pure victims to date. In total, 247 aggressive victims and 168 pure victims were screened from 2,680 Mainland and Hong Kong secondary school students for a oneyear study. Psychosocial traits and behavioral characteristics of aggressive and pure victims were relatively stable and robust across the three time points. However, aggressive and pure victims have different behaviors and internal states after victimization, and they follow different developmental pathways from victimization to reactive aggression. This pioneering study explores the developmental pathways of aggressive and pure victims who later become implementers of reactive aggression. This study extends our understanding of how to apply the SIP model to specific subtypes of victims and measure the emotional and cognitive steps of the SIP model. In addition, this study offers meaningful recommendations specific to Chinese educators and social workers working with aggressive and pure victims.