The invention discloses a medium-speed coal mill. The medium-speed coal mill comprises a motor, a speed reducer, a lower frame body, a middle frame body, a separator, grinding disc assemblies, grinding roller assemblies, a pressurizing device, a pull rod mechanism, a hydraulic system, a slag discharging device, a lubricating system and a foundation; and the improvement of the medium-speed coal mill is that the shape of grinding roller sleeves of grinding parts is in a centripetal arc bowl shape, the grinding molded lines are still arc-shaped, and the curvature radius of the intermediate diameter of the grinding roller sleeves is 0.5 times to infinity times of the pitch diameter of the mill. The medium-speed coal mill has the positive effects that the shape of the original roller sleeves is changed, and the cross section of the roller sleeves is changed from a tire shape into a centripetal arc kidney shape so that the grinding area of the roller sleeves and grinding disc tiles can be increased, the crushing efficiency of raw coal can be improved within unit time, and therefore the output of the coal mill can be improved; and arc-shaped grinding rollers rotate on the grinding disc tiles along the intermediate diameter of grinding rails of the grinding discs, and therefore the linear speed difference value of the grinding roller sleeves and the grinding disc tiles can be reduced, and the abrasion of the outer side parts of the roller sleeves can be reduced.