Abstract: Informal institutions are an important factor that affect the change of agricultural land system. The informal institutions in the change of agricultural land system can be divided into three levels: the values level, the usage-custom-convention level, the village regulations and agreements level.The study found that: when other conditions remain unchanged, the higher the level of informal institutions, the stronger their normalization and binding force, the lower the uncertainty of individual behaviors, and the lower the cost of system operation. When the institutional costs caused by informal institutions are less than the institutional benefits brought by formal institutions, effective institutional changes will occur, and vice versa.It is further found that informal institutions and formal institutions resist each other, conflict, constrain and supplement each other, and jointly determine the evolution path and equilibrium state of institutional change. Informal institutions mainly affect the speed of institutional change. The higher the level of informal institutions, the faster the institutional change will reach the stable state.Therefore, in addition to actively guiding farmers' values and respecting and maintaining the habits and customs that play a positive role in the reform, the government can also take village rules and conventions as an important starting point for the reform.