A repetitive locking/unlocking mechanism based on a Shape Memory Alloy (SMA) wire was proposed to meet the multiple locking/unlocking requirements of the servo system of an onboard laser communication terminal during orbit. First, the working principle of a repeated locking/unlocking mechanism that used a spring component to realize locking and that of an SMA wire output return stress to unlock were analyzed. The locking principle was applied to optimize the locking force and displacement. Second, the locking force was simulated and analyzed. The balance between the unlocking force and the influence of the locking force on the modal of the whole machine was also considered. Finally, a prototype was developed, and the repeated locking/unlocking function as well as the relationships among the unlocking force, unlocking time, and supply current were verified experimentally. Problems such as high temperature, vibration, and different aerospace environments that affect the reliability of the locking mechanism were investigated. Experimental results show that the mechanism can provide a 1 000-N locking force. When a 12 V/3 A power supply is input, the maximum unlocking time does not exceed 2 s. Under an ambient temperature of 90 °C, stable and reliable locking can be ensured, and multiple repetitions of locking/unlocking can be realized. The mechanism has the advantages of being light, small, and repeatable and of having low impact and low power consumption, thus meeting the requirements of multiple locking/unlocking of an onboard laser communication terminal. The mechanism thus demonstrates great application potential.