The invention discloses a device for separating waste mulching films from impurities. The device is characterized by comprising a rotary screening barrel, a fan, a feeding hopper and an outer cover, wherein the rotary screening barrel is horizontally arranged and can rotate around a shaft; a plurality of spiral vanes are arranged on the inner wall of the rotary screening barrel and used for continuously lifting materials to be separated to the position above the rotary screening barrel and pushing large-block impurities out of the front end of the rotary screening barrel; the air outlet of an air flue of the fan is located at an opening in the front end of the rotary screening barrel; the feeding hopper is located at the air outlet of the air flue of the fan; the outer cover is arranged outside the rotary screening barrel. The device for separating the waste mulching films from impurities has the beneficial effects that in the rotary screening barrel, the materials to be separated are continually lifted by the spiral vanes to the position above the rotary screening barrel, the mulching films are blown out of the rotary screening barrel by wind in the falling process, fine impurities like soil are leaked from screening holes of the rotary screening barrel, and impurities like straw are pushed to the front end of the rotary screening barrel through the spiral vanes and then discharged. Therefore the waste mulching films and the impurities are effectively separated.