In order to solve the problems of severe shaking and poor stability of the topping device in the process of cotton topping operation, according to the planting mode of machine-picked cotton field in Xinjiang region, the mechanically-picked cotton field was selected as the research object, a crawler walking system of cotton topping machine based on Beidou navigation was designed, and the design structure and parameters of the chassis and key components were determined. STM32F103 was used as the main controller, equipped with a real-time dynamic difference Beidou navigation system to realize automatic navigation control, and the kinematic model of the tracked chassis was established to determine the preview point, and the curvature deviation between the positioning point and the target path was obtained, at the same time, the speed of the chassis geometric center was introduced as the input of the controller, and a self-adjusting double-input fuzzy PID control algorithm was proposed to realize the automatic tracking of the operating path of the chassis. The results showed that the maximum absolute deviation was not more than 39mm, and the standard deviation was not more than 18.5mm, the average absolute deviation was 15.3mm. The average heading angle deflection angle, the average roll angle deflection angle and the average pitch angle of the topping device were 0.38°, 0.33°and 0.26°, respectively. The self-propelled crawler chassis had strong driving stability, accurate alignment and small tracking error, and can be applied to cotton topping walking operation.