This article mainly studies automatic navigation control methods for agricultural machinery. The navigation system takes RTK-DGPS and inertial measurement unit as positioning sensors. The preview control mode was researched for curve path tracking. The preview control model is to determine the aiming point and calculate the lateral deviation. Automatic turning was realized by fuzzy control method based on genetic algorithm. This control method can online adjust the parameters of fuzzy control using the genetic algorithm, in order to realize adaptive control. Thus the navigation control precision can be improved by the methods studied. The navigation control methods can meet the demand of agricultural machinery operating.