An anti-break lock includes a body and two rods respectively extend from two ends of the body. Two rings extend radially from the body. The body has a passage which communicates with one of the rings and the ring is engaged with an engaging block. The engaging block has a recess in which a pad is received. The passage has a resilient member and a stop pin received therein and the stop pin has a first shoulder and a second shoulder formed in two ends thereof. A contact portion extends from the second shoulder. The body has a room which communicates with the passage. A resilient piece and an engaging member are received in the room. When the lock is damaged, the contact portion is inserted into the recess and stopped by the engaging member so that it cannot move back to its initial position. The lock cannot be unlocked.