The utility model discloses a non-return device for a belt conveyor, which comprises a gear box and a conveyor belt driving wheel, wherein the conveyor belt driving wheel is connected with and driven by the gear box; a one-way wedge block-type overrunning clutch mounted in a non-return end cover is arranged at the high-speed shaft end of the gear box, and is fixed in the non-return end cover through a flat key; and the non-return end cover is fixedly connected with the gear box through a bolt group. As the one-way wedge block-type overrunning clutch fixed in the non-return end cover is used for stopping the reverse operation of the belt conveyor, is simple and stable in structure, small in size and convenient to mount, is matched with the gear box and is connected with a high-speed shaft to stop the reverse operation of the belt conveyor, short-time reverse rotation can be avoided. Therefore, the non-return device is simple in structure and convenient and fast to assemble and disassemble, and is economical and practicable.