Abstract: The heavy-medium separation system of Dongtan Mine Coal Preparation Plant is adversely affected by the presence of oversized particles in its raw coal feed. To cope with this problem, work is made on renovation of the raw coal pretreatment system based on an analysis of the problem encountered in operation. Practice shows that the renovation has led to thorough elimination of oversized particles in raw coal feed, increased reliability of operation of system, dramatic cut-down of labor cost, less difficulty in operation management, and substantially improved economic result.