Abstract: Following an introduction to the property of the raw coal treated by Chahasu Coal Preparation Plant, an analysis is made of the problems of the existing coal washing process. Based on analysis, the ZM high-efficiency mineral separator is used to treat different sizes of small coal after removal of fines, and the result obtained through industrial test is analyzed. The middlings product produced by the separator is re-cleaned. Result of industrial test shows that the ZM high-efficiency separator is well applicable to the cleaning of the small coal of the plant. At the end of the paper, the flowsheet of the renovated cleaning process is proposed.