The utility model discloses an anti-return device for a grinder. The anti-return device for the grinder is used for the grinder. The grinder is provided with a cylindrical grinding chamber provided with a feed inlet (14). The anti-return device comprises anti-return plates (6) which extend inwardly and are disposed at two ends of the feed inlet (14) of the grinder. The anti-return plates (6) are arc plates matching with the wall surface of the grinding chamber of the grinder. By the aid of the two arc anti-return plates, air in the grinding chamber is centralized and moves to a lower screen. Therefore, ground material can be prevented from being blown into the feed inlet to affect feeding performance, feeding environment is improved greatly, discharging capacity of the screen can be enhanced, and production efficiency can be improved. The anti-return device is simple in structure, has high practicability and popularization value, and is especially applicable to grinding of sugarcane leaves.