As the common altitude sub-assembled optical window for a aerial camera with larger view angle has a lower gradient, this paper proposes a protector for the altitude sub-assembled optical window. The mission requirement of the window and its working environments were analyzed, and the protector was designed. A transmission mechanism in the protector was designed and the transmission accuracy was analyzed. Finally, the vibration test and simulated altitude environment test were performed. The analysis and test results indicate that the first natural frequency of the protector is 111.9 Hz, which can ensure the dynamic responce of the protector under dynamic loading. Moreover, the movement of transmission mechanism is stable and reliable in low-temperature (-56.5℃) and low-pressure (5.5 kPa) environments, and the speed error is 1.3%. The protector has been successfully applied in an aerial camera.Experiments show it has effectively overcome the impact of altitude aerodynamic resistance and low-temperature, low-pressure environment, and can be used as a reference for protector designs of other sub-assembled optical windows.