The bag filter has many advantages such as reasonable structure, good sealing, strong circulation, and easy operation. In particular, the side leakage rate of the filter bag is small, the filtration accuracy can be correctly ensured, and the filter bag can be quickly changed, so that the operation cost is lowered. The inner and outer surfaces of the filter are mechanically blasted and polished, which is average and easy to clean. We know that the filtering method adopted by the bag filter is a side-in and side-out method, or a side-in and bottom-out method can be adopted, and the filtering liquid medium is pressed or drawn into the bag filter barrel by the pressure in the pipe. The liquid medium to be filtered supports the filtration of the filter bag supported by the filter blue via electro-polished punching, and the changed solid liquid is filtered to the liquid medium.