The high-altitude long-range gliding UUV is a new conception UUV which includes unmanned aerial vehicle technology and unmanned underwater vehicle (UUV) technology. This paper simulated the three-dimensional flow field of the high-altitude long-range gliding UUV considering its aerodynamic layout using the software Cart3D, which is based on Euler equations. Then the result was amended with a consideration of viscid. From the simulation, we obtained the curves of drag coefficient, lift coefficient, lift-drag ratio, pitching moment coefficient changing with the angle of attack and the curves of yawing moment coefficient, roll moment coefficient changing with sideslip angle. Finally, its aerodynamic characteristics were analyzed. The results show that the layout of the UUV has a large lift-drag ratio, good longitudinal and lateral aerodynamic characteristics and it can meet the needs of gliding.