The automatic self-cleaning filter is composed of a casing, a multi-filter, a backwashing structure, an electric control box, a reducer, an electric valve and a differential pressure controller. The diaphragm in the housing divides the inner cavity into upper and lower chambers, and the upper chamber is provided with a plurality of filter elements, so that the filter space is fully utilized, the filter volume is significantly reduced, and the backwashing suction cup is installed in the lower chamber. During operation, the turbid liquid enters the lower cavity of the filter through the inlet, and enters the inner cavity of the filter element through the partition plate. The impurities larger than the gap of the filter core are trapped, the clean liquid passes through the gap to reach the upper cavity, and finally is sent out from the outlet.