Abstract: The occurrence of environmental mass incidents has brought severe challenges to social stability, which has aroused extensive attention in academic circles. Based on the perspective of resource mobilization theory, and through the comparative analysis of 30 typical environmental mass incidents from 2005 to 2016 found that the mechanism of environmental mass incidents composed of six elements: the specific target for groups, the participation of multiple subjects, the effective group communication, the support of experts and scholars, the spread of mass media and the use of mobilization strategy. Moreover, these six elements have a significant positive impact on the event scale. The higher the satisfaction degree of the six elements is, the larger the event scale will be. Then the countermeasures to govern environmental mass incidents are put forward on the basis of these conclusions, which are to improve public interest expression mechanism, promote open decision-making mode, increase information disclosure, give play to the unique advantages of experts and scholars, enhance the level of the government response and strengthen the effectiveness of institutional norms. These findings have positive significance for the treatment of environmental mass incidents, and also have reference value for effectively preventing environmental mass incidents.