According to the demand of automatic navigation of orchard spraying machine, a navigation control system for spraying robot based on Beidou navigation satellite system（BDS）was designed. The system included RTK-BDS receiver, navigation controller, steering controller, electro pneumatic steering system, three dimensional electronic compass. The closed control loop of steering angle was composed of steering controller, electro pneumatic steering system, three dimensional electronic compass. The closed loop could realize the servo control of steering angle according to control command from navigation controller. The kinematics and dynamics models of spraying machine were analyzed and a lookahead dynamic path search model was established. The input of the lookahead dynamic path search model was lateral tracking error and the output was steering angle from navigation controller. Navigation path planning on the spraying machine was designed according to the characteristics of the orchard, and field tests were carried out in the orchard. The tests were done at different traveling speeds, which showed the offset error became bigger with the increase of traveling speed and the traveling speed of 2 km/h was the optimal speed for quick steering speed and small offset error. The field tests showed that the maximum offset error was no more than 0.13m and the average offset error was no more than 0.03m for straight tracking at the traveling speed of 2km/h. The field tests indicated that the navigation control method was appropriated to orchard spraying machine. 