The invention relates to a prefilter. The prefilter comprises a reversing valve, a scraping and washing component and a filter element component, wherein the reversing valve comprises a valve element, a connecting pipe and a valve cover, the valve element comprises a valve body, a first connecting body and a second connecting body, the first connecting body and the second connecting body are oppositely arranged and are respectively fixed at the two sides of the valve body; the scraping and washing component comprises a cup body and a connecting piece which is rotatably arranged in the cup body, the cup body is provided with a cavity communicated with the through hole, and a convex edge is arranged on the inner wall of the cavity; and the filter element component is arranged in the cavity of the cup body and guides water flow to enter the filter element component by virtue of rotation of the valve body for carrying out filtration or cleaning the filter element component. The prefilter provided by the invention has the advantages that the water flow can be guided to enter the filter element component for carrying out filtration or cleaning the filter element component, so that flow direction of the water flow inside the prefilter is more reasonable; meanwhile, water can be sprayed outward from the interior of the filter element component during cleaning, so that cleaning of the filter element component can be more clean.