Abstract: According to the problem of non-normal operation of slurry treating system caused by unstable of feed quantity of secondary flow sizing screen,treating capacity insufficient and concentration of centrifuge frequency changed in Chengjiao coal preparation,the renovation was done from the four aspects of modifying the underflow pipeline of secondary sizing screen,making the underflow of secondary sizing screen enter into underflow of thickener.Reforming the liquid pool of screen bowl centrifuge and realizing the automatic control of coal slurry treating system,so that achieved the stable operation of the slurry treating system.