A filter is an indispensable device on the conveying medium pipeline. It is usually installed in the pressure reducing valve, pressure relief valve, fixed water level valve, and the inlet device of other equipment of the square filter. The filter consists of a cylinder, a stainless steel strainer, a draining section, a transmission and an electrical control section. After the water to be treated passes through the filter cartridge of the filter screen, the impurities are blocked. When the cleaning is required, the detachable filter cartridge can be taken out and re-loaded after the treatment, so that the maintenance is extremely convenient.