The Ge-film-based photon-counting imaging detector is a key component of optical payload in space weather observation. It's important to study the space temperature adaptability of Ge film since the performances of Ge film are extremely sensitive to the temperature. Herein, the in-situ tests are proposed to measure the resistance and stress of the Ge film at the operating temperature. It is demonstrated that the resistance decreases from 520 MΩ/ to 124 MΩ/ linearly between −20 °C and 80 °C, which can meet the requirement of the imaging system well. And the stress gradually releases in the thermal cycle. The ex-situ test is adopted to investigate the limited temperature adaptability and the intrinsic mechanism of performance variations. When the temperature increased to 600 °C, Ge film failed and cracked because of resistance reducing to 30 KΩ/ and stress increasing to 504 Mpa. Meanwhile, methods were proposed to enhance the temperature adaptability of Ge film by analyzing crystal phase and optical band gap. Thus, the resistance and stress changes of Ge film in space have little effect on the performances of imaging system. The Ge film with high temperature adaptability and low stress we prepared is promising in the space observation.