The invention discloses a safe large vehicle brake comprising a braking bottom plate, a brake shoe and a cam mechanism. The brake shoe and the cam mechanism are mounted on the braking bottom plate, and the brake shoe comprises an active brake shoe body and a passive brake shoe body. One end of the active brake shoe body is connected with the cam mechanism and is expanded and closed in the rotatingprocess of the cam mechanism so as to be attached to a brake drum for friction, and the other end of the active brake shoe body is in transmission connection with one end of the passive brake shoe body. The other end of the passive brake shoe body can be clamped to a sliding groove in the braking bottom plate, and a reset mechanism is arranged in the sliding groove and enables the passive brake shoe body and the sliding groove to be connected. Through improvement of structural design of the brake shoe and a friction piece, the friction piece can evenly conduct friction braking, the service period of the brake is greatly prolonged, the good braking effect of the brake is ensured, the brake is simple in structure and convenient to mount and maintain, and the problems that as for an existinglarge vehicle shoe-expanding-type brake, the braking effect is poor and the use cost of the brake is high are solved.