The present invention proposes a crushing and grading device and method, the crushing and grading device comprises a double-roll
crusher, a screen inclined downward is arranged below the crushing mechanism of the double-roll
crusher, a buffer convex strip is arranged on the screen, the crushing mechanism comprises a fixed roller and a floating roller, the return mechanism comprises an arc-shaped
return channel, the arc-shaped
return channel is located on the outside of the fixed roller, conveyor chains are arranged at both ends of the arc-shaped
return channel, and a scraper plate is arranged between the two conveyor chains; an inclined sliding cleaning roller
brush is arranged on the lower side of the screen, a traction
rope is connected to the end of the cleaning roller
brush, a winding mechanism is arranged at the upper end of the screen, the winding mechanism comprises a connecting frame, a winding gear is rotatably arranged on the connecting frame, a winding wheel is fixed on the winding gear, the traction
rope is connected to the winding wheel, and the connecting frame is connected to the
telescopic cylinder. The return mechanism and the winding mechanism of the present invention shorten the return path of the coarse material on the screen and also facilitate the cleaning of the screen; the material is fully screened by the buffer convex strip.