In order to realize the ground clearance and leveling control of the chassis for the high-gap plant protection machine, a high-gap multi-functional plant protection machine jointly developed by Hunan Agricultural University and Zongnan Heavy Industry was used as a platform to design a chassis automatic leveling system. The system is mainly composed of STM32 main control chip, inclination sensor, drive module, parallelogram lifting mechanism and hydraulic actuator. Each parallelogram lifting mechanism is installed with an inclination sensor, which is used to detect the clearance of chassis from the ground. One horizontal inclination sensor is installed at the center of chassis, which is used to detect the horizontal angle of chassis. Kalman filter algorithm was used to process the dip angle data. Based on the position error control and the angle error control, the leveling control strategy was obtained to achieve the automatic control of the ground clearance and chassis leveling. The test proves that the filtering algorithm can effectively suppress the data jitter; the leveling system can complete the ground clearance adjustment and the chassis leveling; the average response time is 0.45 s, the static average horizontal error is no more than 0.25°, and the maximum error is 0.45°, the root mean square error is no more than 0.27°. The dynamic average horizontal error is no more than 0.64°, the maximum error is 0.81°, and the root mean square error is no more than 0.34°. It is shown that the chassis leveling system meets the requirements of the high ground plant protection machine.