Optical system of an aerial digital camera based on large planar array CCD with 50 million pixels is designed, considering aerospace environment and imaging quality. The focal length of aerial digital camera is 75 mm, F number is 4，and distortion is less than 0.1%. The required working temperature is between -40 ℃～60 ℃. After carefully research on the influence of temperature on imaging quality of optical system, a new approach is put forward. Aerial digital camera can reach excellent imaging quality when soaking in a large temperature change by this new technique. This approach can not only eliminate defocusing effect of optical system caused by temperature change, but also make the aerial digital camera be smaller and less weighty.