For most SMA (shape memory alloy) locking-release devices, they only can complete single function: either locking or release. For their lack, this paper designs a new SMA locking-release device. The device only has one SMA wire, but it can complete two different functions: after being installed the stuck position cover and electrified to the SMA wire, it can complete the purpose of locking; after being moved away the stuck position cover and electrified to the SMA wire, it can complete the purpose of release. In addition, geometric parameters of the center springs and separation springs are designed, and the max release load and reliability of the separation also be analyzed. Based on the proposed design scheme, a new SMA locking-release device is manufactured and assembled. Through the test, it can be known that when the device is used to lock the joint, it's response time is 0.65s under about 5A current; when the device is used to release the joint plate, it's response time is 0.42s under about 5A current. Finally, this paper tests the max preload of the device, and it proves that the device can be used under about 800N.