The medium efficiency filter adopts a new composite non-woven fabric as the filter material. After processing, a plurality of filter bags are formed, and the bag mouth is fixed with a metal frame. The utility model has the advantages that the filter bag can be repeatedly cleaned and replaced conveniently. Widely used in electronics, precision instruments and meters, machinery, metallurgy, chemical, textile, light industry, medicine, food and other departments and general air conditioning system air purification filter. The utility model can also be used as a front filter of an efficient air filter, so as to reduce the load of the HEPA filter and prolong the service life.