Abstract：Social identity, group-based emotions and efficacy are three major social psychological factors that affect people’s participation in a collective action. Previous researches, focusing largely on the disadvantaged groups, examined a single factor at a time and/or explored the relationships among these factors in the offline collective action. Recent studies, however, extended levels and types of factor in their models and attended to the online collective action. The current study attempted to integrate the above three major factors by exploring the moderating effects of multiple social identities in the relationships among group-based emotions, efficacy and participation of different kinds of collective action. Three studies were conducted using different methods. In Study 1, 240 undergraduate students from a university in Tianjin City took part in a questionnaire survey on the Diaoyu Island Event. Study 2 was a questionnaire survey on the Libya Event. and 480 undergraduate students from 6 different universities in Tianjin City were recruited to complete it. Both surveys included demographics in the first part, followed by a questionnaire on different social identities, group-based emotions and efficacies. Study 3 was an experiment 135 female undergraduates were randomly assigned to three different conditions, female identity primed group, school identity primed group and the control group. Participants then completed a questionnaire on their attitudes toward potential gender discriminations faced by job applicants. Data was collected and analyzed using SPSS 13.0 and Lisrel 8.70. Results indicated that group anger had a significant positive effect on offline collective action participation; and efficacy had a significant positive effect on both offline and online collective action participation. The above effects were further moderated by different social identities. Specifically, identification with a large social category of event affected behavior tendency by moderating emotional path (and rational path some times), and identification with the organization of collective action affected behavior tendency by moderating rational path only. Findings suggested that people were rather rational in their participants of the online collective actions.