The existence of aggressive behavior in autism spectrum disorders (ASD) raises questions about whether cognitive and emotional factors in social information processing play a role between autistic traits (ATs) and aggressive behavior in the general population, especially in the context of Chinese culture. Moreover, given a possible gender difference in these variables, the study aimed to examine the effect of ATs on aggressive behavior, and the potential mediating role of hostile attribution bias and alexithymia on this association, as well as gender difference. 850 Chinese college students participated in the assessment, including their ATs, hostile attribution bias, alexithymia, and aggressive behavior. Pearson correlation, mediation effects analyses, and multiple-group comparison were conducted. The results indicated that ATs indirectly predicted increased aggressive behavior through attribution bias and alexithymia. Gender difference in mediating effects was revealed: ATs indirectly predicted increased aggressive behavior through the serial mediating effect only in males. Hostile attribution bias and alexithymia completely mediated the association between ATs and aggressive behavior, which contained the separate mediating effects of (a) hostile attribution bias and (b) alexithymia and the serial mediating effect of (c) hostile attribution bias and alexithymia. Gender differences in mediating effects were found only in the serial mediating effect, which was significant in males but not in females. The findings revealed the internal mechanism of ATs affecting aggressive behavior and gender difference, which have implications for the intervention of aggressive behavior of individuals with autism and those with high levels of ATs.