To determine the community stability of arthropods and the dynamics of Mason pine caterpillars (Dendrolimus punctatus Walker), the cusp catastrophe models were developed based on diversity index, richness index, evenness index of defoliators, predators, parasitoids, sap sucking insects and the ratio of pests and natural enemies in Daqing Mountain in Guangxi Province during a complete outbreak of Mason pine caterpillars. The models were tested with data of Guiyang in Hunan Province. The results showed that during the outbreak process of the pine caterpillars, the arthropod communities in the outbreak areas were apparently unstable; in the non-outbreak years, the arthropod communities in the outbreak areas were in a sub-stable state; in the non-outbreak areas, the insect communities were in a sub-stable state in outbreak years, and the arthropod communities were apparently in a stable state in non-outbreak years. During the increasing phrase of the pine caterpillars, the non-stable state of communities would most likely lead to their outbreak. During the declining phrase, if the system was still in a non-stable state, it would also lead to consecutive outbreak, depending on the effects of various factors. The outbreak takes on nonlinear and catastrophic characteristics. Defoliators are the most important regulating factors. A system with various groups evenly related is relatively stable. Pest outbreaks are the expression of the arthropod communities that tend to be stable. This study demonstrates that the cusp catastrophe models can be applied to forecast the stability of arthropod communities and the dynamics of Mason pine caterpillars.Key Words: mason pine; Dendrolimus punctatus Walker; cusp catastrophe model; community; stability