Abstract: A flying vehicle is in serious physical and thermal environment when passing through aerosphere, which might be treated as a structural elastic problem, where the modal characteristics are very important inputs of the problem. Traditionally, it is difficult to simulate the environment in the modal testing, however, the realistic modal parameters of a hypersonic flying vehicle could be obtained easily by the operational modal analysis (OMA) technology. The background and the development of the operational modal analysis are reviewed in the paper, and the PolyMAX algorithm is specially addressed. The load measurement data from a flight test of a flying vehicle is processed, the modal parameters are identified successfully based on the PolyMAX method, and the modal parameters are validated.