Self-sacrifice is universally considered to be a noble virtue among social norms. The identity fusion theory illustrates why some people pursue pro-social goals and can identify who is more likely to commit on self-sacrifice by using imagery scenarios or self-report measures. Despite the abundance of the evidence about the self-sacrifice aspects of fused individuals, very little is known about how identity fusion performs on important psychological aspects, such as well-being. Thus, I extended previous research to bridge the gap between identity fusion, well-being and pro-group behavior with a real-world social protest happened in Taiwan. A total of 1,785 participants were recruited through internet during the period of the social protest. Results showed that the degree to which people who are fused with groups, including country and family, was positively correlated to well-being and pro-group behavior. In addition, the visceral feeling of oneness with family mediated the link of fusion with country and individuals’ well-being, but suppressed one’s attitudes toward protecting Taiwan. The role of family on identity fusion would be discussed from a perspective of collectivistic cultures.