The cylindrical screen is mainly composed of a motor, a reducer, a drum device, a frame, a sealing cover, and an inlet and outlet. The drum device is installed obliquely on the frame. The motor is connected to the drum device through a coupling via a reducer, driving the drum device to rotate around its axis. After the material enters the drum device, due to the tilt and rotation of the drum device, the material on the screen surface flips and rolls, causing qualified materials (undersized products) to be discharged through the discharge port at the bottom of the rear end of the drum, and unqualified materials (undersized products) to be discharged through the discharge port at the tail end of the drum. Due to the flipping and rolling of materials inside the drum, materials stuck in the sieve holes can be ejected to prevent blockage of the sieve holes.