With the continuous development of coal preparation technology and the continuous improvement of the development requirements of clean and efficient utilization of coal, the slime water system of coal preparation plant has become an important part of restricting production efficiency. Aiming at the problems of low separation efficiency and poor classification effect of slime water system in Xipang Coal Washing Plant, this paper combed the process of slime water. Through a large number of process effect evaluation tests, some problems existing in the separation and flotation of coarse slime were analyzed. The process adjustment and test analysis of the size of the sieve seam of the raw coal desliming screen and the direction of the slime water were carried out. The process indexes of coarse slime separation and flotation were gradually improved, the separation efficiency was improved, and the recovery rate of clean coal was increased by about 2 %.