According to the partial equilibrium theory, this paper built an agricultural equilibrium model which was used to simulate the impacts on the market price of agricultural products due to the occurrence of natural disasters. This model was used in the case study area, the quake-hit region Wenchuan, to simulate and evaluate the influences on market price fluctuation of agricultural products nationwide on the basis of data from Sichuan provincial statistical yearbook, survey data in the quake-hit region and data supplied by relevant agencies for the local government and departments concerned. The simulation results indicate the Wenchuan Earthquake has had only marginal impacts on the fluctuations of market price of agricultural products such as rice, wheat, corn and pork and have had no strong disturbance on the stability of the prices of agricultural products at national level. Wenchuan Earthquake, however, undoubtedly, resulted in some effects on the local agricultural production. It brought significantly negative impacts on both planting industry and breeding industry in the severe disaster areas. The research results of this paper provides information of decision-making for the disaster areas in scientifically evaluating earthquake influences on the changes of market prices of agricultural products, laying down planning of earthquake preparedness and disaster reduction and the recovery of agricultural production for the quake-hit region.