The rotary drum screen is a special screening device that realizes material classification and impurity removal through the low-speed rotation of its cylinder. Driven by a motor and reducer, the drum performs uniform rotary motion. Screens with different aperture sizes are installed inside the cylinder. After materials enter the cylinder, they tumble and slide along with the drum body. Fine materials pass through the screen meshes for separation, while large impurities and bulk materials are discharged from the tail end of the cylinder, completing multi-stage classification, desliming and impurity removal operations. The complete machine features a simple structure and stable operation.