The automatic fuzzy algorithm for controlling tilling depth of tractor based on slip rate was simulated. Firstly, the mathematical of the system was built and simulated by using Matlab/Simulink. Secondly, the fuzzy controller was designed. Further simulated analysis of the proposed model was carried out. At the same time, PID controller and fuzzy-PID controller were also designed and simulated. And then, these three controllers performance was compared, including responsiveness, adaptability, and anti-interference performance. As a result, fuzzy-PID and fuzzy controller was more suitable for this system, but fuzzy-PID needed more variables and seemed more complex.