Community residents are important one of stakeholders for sightseeing places. Based on Theory of Reasoned Action and Social Exchange Theory, the case study of 2013 China Flower Expo in Changzhou uses Smartpls 3.0 software to explore relation between residents' perception of event tourism impact and supportive behavior, and the structural model based on overall attitude as a mediator variable is tested. The results showed that:1)Residents' positive perception towards event tourism has significant positive impact on residents' attitude, while the residents' negative perception towards event tourism has significant negative impact on residents' attitude. Residents' overall attitude has an obvious positive effect on residents' supportive behavior; 2)Overall attitude plays a mediating role in residents' perception and supportive behavior towards event tourism; 3)Residents' supportive behavior for event tourism depends more on the positive perception than on the negative perception; 4)Residents in Changzhou have paid more attention to the social-cultural impact of China Flower Expo; 5)The government and the event tourism management institutes need to improve the positive impact to residents rather than avoid the negative impact of event tourism.