The utility model relates to a bottom plate device for a semi-autogenous mill cylinder. The bottom plate device for the semi-autogenous mill cylinder disclosed by the utility model is composed of a bottom plate body, an upper plane, a lower plane, a groove, a side surface, a matching device, a lifting lug and a suspension hole. According to the utility model, the replacing period of an integral cylinder lining plate is prolonged; the production cost of the integral cylinder lining plate is reduced; a grinding medium and the material motion state are ensured to be continuous and steady; therefore, the grinding efficiency is increased; the bottom plate device for the semi-autogenous mill cylinder has universality and good abrasive resistance and has the characteristics of replacing bottom plate specificality and the like; and furthermore, the stability of the material motion state in the cylinder can be kept.