Abstract:The community dynamics and stability of insects in masson pine forests is discussed by analyzing the outbreak process of pine caterpillars (Dendrolimus punctatus). The community with high diversity, especially that during the endemic phase, tends to be more stable. Diversity of folivorus group plays an important role in the diversity and stability of the whole community. Predators mainly affect on sap sucking group, while parasitoids on defoliate group. Some insects neither phytophagous nor natural enemies can also play a role to certain degree. Diversity at the increase phase is the biggest, and if it is big enough,outbreaks of pine caterpillars can be suppressed,otherwise the outbreaks can occur. Increase of phytophagous diversity leads to more parallel connections and enhances the control feedback of the system. Complexity of parallel connection structure can turn to stability,whereas series connection can not.