The frequent occurence of rat (Microtus fortis) disaster in Dongting Lake Area, which induced great loss on agriculture. Based on the ecological theory, the software STELLA for systematic dynamical analysis was used to simulate the rat population change in Dongting Lake area. An age-structured dynamic model for rat population change was constructed. By imitation analysis, the characteristics of rat population change was studied, and the general rules and the catastrophe process of its population dynamics were discussed. The research indicated that the influence of the birth rate and death rate on population growth was significant, but the initial population was not the key factor. Some control strategies of rat disaster in Dongting Lake Area were proposed. We suggested to use biological methods, such as restoring the natural enemies of the rat in the Lake area, to increase the biodiversity, so as to control the rat disaster.