Automatic guidance control plays a important role in modem production agriculture because it can improve the precision and reduce the labor cost in various field operations such as field preparation, planting, spraying of chemicals, fertilizer application, weed control, and harvesting.However, the complex of agriculture environment and accurate operating requirements ask for real-time navigation control parameters adjustment.In this paper, we propose a universal navigation control parameters tuning method base on AutoTrac.The John Deere's AutoTrac, which incorporates a GPS receiver and controls the vehicle's steering wheel, is a low-cost auto steering system designed for various field operations.AutoTrac has many controller parameters that need to be tuned for different working conditions (e.g., soil properties, operation speed) to keep the machine on the desired path or to approach the desired path as quickly a.s possible without too much overshooting.The current controller parameters include steering sensitivity, line sensitivity tracking, line sensitivity heading, acquire sensitivity, curve sensitivity, steering wheel speed, steer play, heading lead, and steering response rate.Currently, these parameters are manually tuned by the machine operator, which is inconvenient and time-consuming for the average operators.John Deere XUV825i gator choose as the vehicle platform in this paper for its excellent off-road performance convenience for different terrain test outdoor.Mechanical and electrical modification are needed on the gator ensure regular operation of AutoTrac.Follow operation manual, we first study the influence of steering sensitivity under typical straight line navigation mode.We did the tests under RTK-DGPS signal with constant speed and other navigation parameters only changed steering parameter and initial attitude in different terrain.Steering sensitivity is range from 50 to 200 with adjustment interval 10.Five different initial attitude was set in the test, which are overlap with AB base (straight line base) , 0.5 meter tracking offset with AB base on left and right,30 °heading offset with AB base on left and right.Accurate AB base(the projection of GPS receiver on floor) and 3D vehicle trajectory was acquired by real-time latitude, longitude and vehicle attitude information through 3D coordinate transformation.Tracking offset, heading offset and entry time was figured out to evaluate the influence of steering sensitivity on AutoTrac.Then orthogonal experiment was design to test other control parameters such as line sensitivity tracking,line sensitivity heading, acquire sensitivity, etc.At last, other navigation mode such as curve navigation mode was tested in the same way.Experiment results show that initial attitude will affect system's performance and the effect of tracking offset is more severely.Uneven land need higher sensitivity and steering sensitivity is more effective among other navigation control parameters.What's more, AutoTrac work stable under different terrain condition and more than 80% are under system accuracy (plus-minus 2cm).The method we have propose here is suitable for other automatic navigation system and do the spade work for further development of adaptive control system of navigation control parameters in autonomous navigation systems.