In the key period of social transformation, “institutional slowness”leads users to look for non-institutionalized interest expression channels, resulting in network group events , and even Street group violence,which may cause serious negative effect to society. Recently, The academic circles have been going on a deep analysis on network group events’ concept、 characteristics、causes、prevention and resolution of the events. based on the network group events connotation as well as the occurrence mechanism,this article focuse on network group event mechanism: stimulus response mechanism、 mechanism of identity、 filtering mechanism、induced from diffusion mechanism. The prevention and solution of network group events have important realistic significance and social value.