Abstract: Based on the integral separation PID control algorithm of single chip microcomputer, the automatic control system of harvester is designed. The STC12C5A60S2 is taken as control core of the system, and the relevant data and information are collected through the detection module of the threshing cylinder rotation speed signal, the test module of the grain feed, the detection module of threshing drum torque and the speed module of the seed auer shaft with the system internal coordinated integrated algorithm processing. Then the corresponding control signals are sent to electric putter in real-time, and the best integral walking limit value β of the harvester control system is to achieve the optimal state by regulating its AD value for driving HST. In addition, the sudden situation of the process of harvester operation could be dealt with such as overload, slow down speed or block rotation in real time. At last, the control effects of the traditional PID control algorithm and the integral separation PID control algorithm with three different integral separation limits are respectively completed through the simulation test and comparison experiments. The simulation results showed that the optimal design of mechanical control system based on integral discrete PID control algorithm must be based on traditional PID control algorithm, and the optimal parameter ratio is adjusted appropriately.