Abstract: A process of prescreening before grinding has been added for a copper ore with high slime content in Xinjiang.In order to evaluate the effects on practical production,the particle size composition of the raw ore,oversize fraction and undersize fraction of screening,the discharge from a ball mill and the overflow and underflow from a hydrocyclone was analyzed.Compared with without prescreening,adding of the process is beneficial for technical and economical indicators,such as promoting the utilization factor of a ball mill,reducing energy consumption and increasing the productivity.The successfully utilization of the process of prescreening set an example for the concentration of high slime content or fine-grained ore.