The liquid flows in from the filter inlet (1) and flows inward from the outer surface of the filter element (6). The lower end of the filter element is connected to the outlet (2), and the liquid flows out from the outlet; when a certain amount of impurities is intercepted on the surface of the filter element, timing or as set The cleaning procedure is started at a constant pressure difference. The geared motor (4) drives the scraper (7) obliquely attached to the outer surface of the filter element to rotate to scrape off the impurities on the outer surface of the filter element. The impurities leave the surface of the filter element along the scraper and fall with the descending liquid. Into the bottom of the filter, the rotating sweeping plate sweeps the bottom heavy impurities into the sewage collection chamber (5), the impurities accumulate in the sewage collection chamber and the bottom of the filter, the sewage valve opens automatically at regular intervals, and the liquid containing high concentration impurities is discharged from the sewage outlet (3) ) Discharge, if necessary, the discharged residual liquid can be recovered.