Strainer is an indispensable device on the transmission medium pipeline, usually installed in the pressure reducing valve, pressure relief valve, fixed level valve, square filter and other equipment of the inlet end equipment. The filter is composed of a cylinder, a stainless steel filter screen, a blowdown part, a transmission device and an electrical control part. After the water to be treated passes through the filter cartridge of the filter screen, its impurities are blocked, and when it needs to be cleaned, as long as the detachable filter cartridge is removed and re-loaded after treatment, therefore, the use and maintenance are extremely convenient.