Agricultural insurance system plays a vital role in the development of regional agricultural economy. With the government's promotion of income insurance with higher level of security, the role of agricultural insurance in production will continue to strengthen. However, due to the information asymmetry between the insured farmers and insurance companies in the agricultural insurance market, it often causes the moral hazard of the insured and seriously affects the operational efficiency of policy-based agricultural insurance. On the other hand, our country's legal system of supervising and punishing the moral hazard of the insured is not perfect, and it is easier to induce the moral hazard of the insured. In this context, it is of great significance to improve the design of moral hazard prevention mechanism of agricultural income insurance. In 2019, document No. 1 of the Central Committee clearly put forward that the agricultural insurance policy should be improved and the pilot projects of income insurance for rice and maize should be promoted. Income insurance, as an important development direction of agricultural risk management in China, operates more professionally and transparently, which can effectively avoid the shortcomings of the food price system. At the same time, the insurance guarantee level is higher, which can divert the risk of production and market price faced by agricultural producers, and the premium rate is lower than that of single price and income insurance. But at the same time, income insurance can give moral hazard incentive to the insured peasant households. In the event of large-scale natural disasters, insurance companies are unable to conduct on-the-spot surveys to grasp the actual losses caused by disasters. Farmers can falsely report their own income after the disaster and seek high compensation. Because of information asymmetry, information dominant party often produces adverse selection behavior with moral hazard, which affects the normal development of agricultural insurance market. Based on the corn income insurance clause of Hebei Province and the experience of American agricultural income insurance, this paper designs insurance contracts with higher level of protection, which can effectively reduce moral hazard incentives. The mathematical model considers the influence of market price fluctuation, farmers' own disaster losses and insurance mechanism factors on the moral hazard incentive degree of income insurance, which greatly enhances the practicability of the model and makes the model more fitting to the analysis of practical problems. The model depicts the information of insured peasant households in depth, and takes the final total income of peasant households as a measure factor to study the choice of peasant households in the process of production and insurance decision -making. The simulation results show that if the premium payment mode is not improved, the income insurance will generate moral hazard incentives for the insured farmers. When the market price is lower or equal to the price of insurance contract for compensation for loss, moral hazard incentive effect is particularly obvious. On the basis of this conclusion, this paper establishes a mathematical model with incomplete information dynamic game, and corrects the loopholes of moral hazard in the design of insurance mechanism by analyzing the maximization of farmers' utility and the thinking logic of farmers' risk consideration. Finally, the retrospective premium payment model is adopted to improve the insurance contract and reduce the moral hazard incentives that may arise from agricultural income insurance, which will contribute to the healthy development of policy -based agricultural insurance in China.
