Multi-stage filtering device in front of screen pump

A screen type multi-stage filtering device in front of a pump comprises a floating platform, a filtering device, a filter cartridge rotation driving device and a water lifting device, the filtering device comprises a first-stage filter cartridge, a second-stage filter cartridge and a rotating shaft, the second-stage filter cartridge and the first-stage filter cartridge are coaxially and vertically arranged, the bottoms of the two-stage filter cartridge are sealed through a sealing base plate, and the top ends of the two-stage filter cartridge are open; the rotating shaft is arranged in the center inside the secondary filter cartridge, and the bottom of the rotating shaft is fixed on the closed chassis; the floating platform floats on the water surface and comprises a first floating box, a second floating box and a filter cartridge support which are arranged at the two ends of the filter device respectively, the two ends of the filter cartridge support are fixed to the top ends of the first floating box and th