Abstract: Timely and moderate automatic irrigation based on the water requirement level of rice is a water-saving and energy-efficient way to increase the yield and improve the quality of rice. But water requirement level varies during the different period of rice growth and this makes it very difficult to implement automatic irrigation in rice field. This study took the field humidity and water requirement level obtained by using humidity sensor and stylus respectively as the automatic irrigation index, humidity and the change rate as inputs and the irrigation time as output to build a fuzzy control system. This system uses pump as control unit to achieve automatic irrigation. Simulation irrigations and pilot study show that the control process of the system is stable. Compared with artificial irrigation, this system can save water by 10%. The research work can provide a reference for timely, moderate and automatic irrigation of rice.