In order to systematically verify the ability to a domestic small bypass ratio turbofan engine in rainy days in application, a subject of study with an aero-engine being installed is made. And an adaption of test flight for three test systems is performed respectively, i.e. an engine water swallowing test with installed conditions, a simulated slippery running splash test in rainy day, and an adaptability of test flight in rain. In the test there is involved some surge under the conditions of installed water swallowing , and the engine is operating normally in the process of the splash test and the adaptability of test flight in the rain. The test results indicate that the designed engine rain environment verification technology can effectively identify the surge risk of engine after water swallowing, and systematically verify the engine's ability to use in the rainy day environment.