Based on the model of private supply of public goods, the paper develops an analytic framework, which can demonstrate the local government dominated by private reason playing game with the whole reason in the process of protecting cultivated land. Then the paper applies the framework to explaining the policy invalidation and the desire differences between different local governments in the current practice. The results show that the game behavior of local governments dominated by private reason is one of the main reasons for policy invalidation;The developed local governments in the east have a stronger desire for cultivated land protection than the developing ones in the west, and construct a market to deputize for protecting cultivated land in other areas which can make this desire realize.