Abstract: In this paper, U.S. anti-gravity device's basic structure and functions of the composition are analyzed by information of Area 51 and Area 52 and by secret files achieved by hacker Gary McKinnon. The structure and functions can satisfy with the theory of electromagnetic eruption. Therefore it is suspected that U.S. anti-gravity device was produced by electromagnetic eruption principles. In the latter part of the paper, some current technical bottlenecks of the anti-gravity device are analyzed, and our expectations of China's more in-depth studying in this area are raised. Keywords: Flying saucer, Anti-gravity device, Electromagnetic eruption, Principle