The invention relates to a disc brake for a belt conveyor, which comprises a piston, a brake shoe, a brake carrier, a disc spring and a displacement sensor, wherein the brake shoe is fixed in a brake shoe support seat, the middle part of the brake shoe support seat is a groove, a stepped blind hold is formed on one side of the brake carrier, an end face key is arranged at the middle part at one end on the side of the blind hole of the brake carrier, a cover plate is fixedly arranged at the open end of the brake carrier, a thrust plate is sheathed on the tail part of the piston, support pillars penetrating the brake carrier are symmetrically fixedly arranged above and below the thrust plate, the other end of each support pillar is fixed on the brake shoe support seat, and the piston is not directly linked with the brake shoe support seat, but is linked with the brake shoe support seat through a regulating nut, the thrust plate and the support pillars. The brake shoe support seat is linked with the brake carrier through the end face key, and the braking force is transferred to the brake carrier through the end face key and further transferred to a frame, thereby leading the piston to be free of any radial force. A flange of the piston and a brake carrier hole adopt a positioning steel sheet which is pressed in by relying on spring force under the brake releasing state, thereby preventing the abnormal brake and having the advantages of compact structure, reliable performances, convenient regulation, good braking effect and low cost.