After more than half a century, the spreader has developed,while its cab tuning system is still manual controlled and the control precision is poor. In order to improve the control accuracy, the manual control was improved and a kind of automatic tuning system was designed for cab based on the improved system.According to its working principle and structure parameters, mathematical model and AMESim simulation model were established for the automatic tuning system of cab. The original system, the improved system and the automatic control system were simulated. The simulation results prove that the improved system stability is better than the original system, and the feasibility of automatic leveling system is verified. The experiment cost is saved.It provides theoretical basis for the improvement design of cab tuning system.