TWith the application of the work team, workplace bullying in team situations become the focus of researchers and managers. Team members are different in gender and region. Power imbalance caused by these social identity differences between employees in teamwork will lead to further escalation of interpersonal conflict into workplace bullying. The existing theoretical models for explaining the cause of workplace bullying mostly emphasis factors related to the organizational characteristics and job characteristics, ignoring the effects of group interpersonal interaction. Based on social identification theory and self-categorization theory, the social identity differences in gender and region force the individual into a stressful situation. If the individual's assessment of identity differences is stressful enough, and cannot adjust himself or herself to adapt to the new environment, he or she is more likely to be bullied. So we hypothesize that the bigger the difference from the other members of the team in gender or region, the individual is more likely to be bullied. Meanwhile, team identity can trigger employees to seek social support within the organization, thereby reducing the negative assessment of workplace bullying. So we also hypothesize that team identification plays a mediating role between social identity differences and workplace bullying. The present study examined the frontline staffs’ social identity differences influence on their perceptions of workplace bullying and the mediating role of team identification, using a sample of 331 frontline staffs from 22 production teams in four manufacturing enterprises in China. A structured questionnaire was employed as the research instrument for this study. It consisted of five scales designed to measure the variables of workplace bullying and team identification. All scales were well-established in the literature. The social identity differences are calculated by Euclidean distance. SPSS 21.0 were adopted to perform a series of statistical analyses. Hierarchical regression mode was used to test the hypotheses. The results of this study show that gender differences and geographical differences have significant influence on the five dimensions of workplace bullying. The mediating role of team identity in the relationship between social identity differences and the five dimensions of workplace bullying are different: On the dimension of deprivation of rights, it does not have intermediary effect, but it plays a complete mediating role in the relationship between gender differences and social exclusion. According to the research conclusions, this study puts forward some suggestions and implications for future research: In order to reduce the incidence of workplace bullying, managers should pay more attention to the majority of the team's influence on the minority and the threshold ratio of minority groups. For the employees' mental health management, managers need to pay attention to the basic unit of the "team", form team identity through effective new employee socialization strategy and transformational leadership and reduce the incidence of workplace bullying events. In view of the deprivation of rights cannot be changed by team identity, the establishment of employee participation in the management system and the upward feedback communication channels, may be an important way to improve workplace bullying situation.