Abstract: To solve the problems of high content of fine and ultra fine particles in the feed of thickener this caused the poor performance in process of settling and press filtration,seriously limited the process capacity of Pingshuo No.2 colliery coal preparation plant,the paper on the basis of laboratory settling test combined with production practice,using the TDX1220 and TDN2140 mixed agent,that made the efficiency of thickener increased to 88.39%,solid content in over flow decreased to 3 g/L,and daily treating capacity increased to 4.6 t,obtained good effect.