The present invention relates to a changeable combined mechanical key, belonging to the technical field of key structures of encryption locks. The changeable combined mechanical key includes a bracket detachably connected to an end of a key handle, and a protective cover detachably connected to the end of the key handle and a key-shaped component. The present invention achieves anti-theft and duplication-preventing purposes for a key, and has unique advantages in many important fields such as safety boxes, important military places, banks, household intelligent anti-theft locks, and any other fields that require secrecy security. Unlike an electronic key that is easy to cause a problem due to an electronic circuit device and software and so on, the present invention, which is irreplaceable and has changed a machining process of a traditional mechanical key, saves energy and reduces consumption, and has a broad application prospect.