To obtain both good performance on both aerodynamic and stealthy, integrated design and analysis on aerodynamic and stealthy characteristics for flying wing unmanned aerial vehicle(UAV) is conducted based on stealthy inverse design method, focusing on the big bump in the fuselage of twin-engine layout flying wing UAV. Then a kind of fuselage with leading edge similar to eagle mouth is proposed, whose leading edge radius of airfoil is decreased. Using computational fluid dynamics (CFD) method, the numerical simulation is verified on M6 wing. Physical Optics (PO) and Multilevel Fast Multipole Method (MLFMM) are chosen for numerical study on the stealthy performance of cylinder and a certain scale model of flying wing UAV. Moreover, the verified methods are applied to study the aerodynamic and stealthy characteristics of flying wing UAV. The results show that the aerodynamic and stealthy calculation result is close to the experiment data, indicating that the numerical simulation method is valid. Not only the longitudinal aerodynamic performance of flying wing UAV with fuselage leading edge similar to eagle mouth increases appreciably, but also its stealthy performance improves significantly in the forward direction with the azimuth angle from -25°~25°. In addition, it indicates that the stealthy inverse design method is effective. The design with leading edge similar to eagle mouth mainly affects the pressure distribution of fuselage, and it is helpful to advance the lift/drag characteristic. At the same time, the stealthy performance of the optimize design is better than the traditional blunt leading edge at different frequencies and rolling angles.