The manual adjustment control used in the heavy-duty sorting process of Dongzhouyao Coal Preparation Plant was poor. In order to optimize the quality of sorting, an automatic control system was established to control the heavy-duty sorting process. The heavy medium sorting process was affected by the density of heavy medium suspension, the level of the combined tank level, the slime and the water supplement. The automatic control system consisted of the upper machine, the actuator, the sensor and the controller, and regulates the factors affecting the heavy media separation. Comparing the sorting effect before and after use, the sorting effect under the automatic control was more excellent, and the problem of heavy medium sorting control in the coal preparation plant was solved.