Abstract: In modern high-tech war, improving the stealth performance of fighter is one of the important guidelines of fighter design, which directly affects the survivability and combat effectiveness of fighter. Radar Cross Section (RCS) of aircraft is one of the important specifications for evaluating stealth performance of aircraft. In this paper, the digital model of a stealth aircraft is established based on the public report information of it. The aircraft RCS at 10 GHz frequency, horizontal polarization and vertical polarization, with pitch angles of 0o, 5o, 10o, 15o, 20o, 25o and 30o respectively, and with vertical tail, are analyzed by using multilevel fast multipole algorithm. Based on the analysis results, some measures for reducing radar cross section area of aircraft are systematically analyzed.