Combine harvester have to be operated in a wide range of field condition which may induce varying feeding rate. Forward speed is a main variable to control the feeding rate of combine harvester for high efficiency. In this study a control strategy based on optimum threshing power consumption model was developed and integrated into a speed control system for combine harvester automation. A conventional self-propelled combine harvester (Xinjiang-II) was equipped with multiple sensors to collect online information, including forward speed, threshing drum torque and speed. Forward speed was then adjusted by an electric-hydraulic unit based on designed PID controller to achieve an optimum range of threshing power consumption. Field test was conducted to evaluate the performance of the controller under variable feeding rate condition. From obtained results, the controller can improve the efficiency of tested machine during field operation.