Abstract: It has been found that the troubles faced by Nantun Coal Preparation Plant in its operation of the jigging system involve difficulties in washwater management and control of liquid level,as well as unstable reject extraction operation. Such being the case,technical transformation work is made on the jig and the jigging process. Through the reform of the slurry piping system,and addition of hydraulically controlled reject discharge gate and liquid level control device,the jigging system is now enabled to operate with internal circulation of washwater and automatic control of reject discharge and liquid level,ensuring,as a result,the smooth operation of the overall jigging system.