Abstract: In order to improve the coal sorting efficiency of coal preparation plants, a design scheme for an automatic control system of ash content in dense medium sorted clean coal is proposed. Firstly, the overall framework of the automatic control system was introduced, and then the design of the main functional modules such as online ash detection, ash prediction and SPC analysis, and closed-loop control algorithm were analyzed in detail. Finally, the application effect of the automatic control system was verified through practical application. Through practical application observation, it can be found that after adopting the automatic control system, the ash content of clean coal is basically stable within the range of 10.6% to 11.2%, which meets the prescribed requirements （10.5% to 11.5%）. The automatic control system can be widely promoted, providing important assistance for improving the coal sorting efficiency of coal preparation plants.