Abstract: The present disclosure provides a head replaceable electric tool with a safety mechanism, which has a tool body and at least one working head, the working head is detachable; the tool body has a machine body housing, a motor mounted in the machine body housing, and a working head engagement device arranged at an output end of the tool body; a switch body is arranged on the tool body; a button is arranged on the switch body; a locking device is arranged in the tool body; a main body of the locking device is arranged in the machine body housing and is arranged concentrically with the working head engagement device; the locking device is connected to an inner wall of the machine body housing through screw threads or a slope; and a safety mechanism for locking the button is arranged between the tool body and the working head.