Mass incidents are the result of game between different interest groups.In the mass incidents,the change of group power especially the people's strength plays an important role in the evolution course of social conflicts. In this thesis，we use evolutionary game model to illustrate the evolution course of social conflicts depending on the change of group power，and divide it into four stages:incubation，acute，outbreak and recession. The most effective way to deal with mass incidents is to try to reach a compromise agreement between the people and the local government，which can be realized by active negotiation between the two groups or an intervention of a third party. In addition，in order to prevent the mass incidents，the government should strengthen the information collection system，promptly solve the people's interest problem，using media to guide，and increase the transparency of the government's work.