This paper adopts prospect theory to build the prospect value matrix of business behavior of insurance company which is supervised by government departments in agricultural insurance market, construct the influencing model of insurance company's behavior under the condition of financial subsidy, gain the conditions and ways to reduce non-normative operation of insurance company, and explore its causes based on real cases. The results show that the cost of normative operation, benefit of irregular operation and penalty from government supervision will significantly affects behavioral choices of insurance company. Because of different risk aversion coefficient, there are differences in the attitudes of insurance companies to operating risk of agricultural insurance, subsidies cannot completely and effectively reduce the non-normative behavior of insurance company, and even have a negative effect. At present, inadequate supervision and insufficient punishment form government departments are the main reason for the non-standard operation of insurance companies. The government can strengthen supervision and intensify punishment to operating behavior, and insurance company can increase the quality and efficiency of agricultural insurance supply by improving the grass roots service system and using advanced scientific and technological means.