This paper analyzes and researches the RAT generator natural icing flight test of a type of domestic aircraft in its development process. Firstly, this paper introduces the reason and purpose of the RAT generator natural icing flight test, and the civil aviation standards for natural icing environment. Secondly, the paper introduces the flight test method for RAT generator natural icing flight test. Finally, the test results are analyzed. The results show that RAT generator flight test of natural icing environmental condition meet airworthiness regulatory requirements, RAT generator manual release function can be realized in the foreseeable natural icing environmental condition, and the power supply function is normal.