Abstract: A flip-out tail fin is designed to improve the shooting quality of the fin-stabilized shell of small length-diameter ratio. Three fin-stabilized shells with fins of the same shape and different aspect radios are simulated numerically by applying the AUSM+scheme. The shear stress transport turbulence models and the lower-upper symmetric Gauss-Seidel implicit method are used to solve the 3D Reynolds-averaged Navier-Stokes equations. The differences in the aerodynamic coefficients and the aerodynamic characterstics of the projectiles when the Mach number varies from 1.5 to 3.5 are obtained and analyzed, and the applicability of fins of different aspect radios is discussed. The calculation results indicate that the lift-to-drag ratio of the C-type shell is 7% greater than that of the B-type shell in the region where the Mach number is close to 1.5; as the Mach number is above 2.5, the lift-to-drag ratio of the A-type shell is greater than that of the B-type shell and the C-type shell; the lift-to-drag ratio of the A-type shell is 5.4% greater than that of the B-type shell in the region where the Mach number is close to 3.5. The pitching moment coefficient rises in absolute value when the Mach number gradually increases, the rising trend increases with the increase of of the aspect ratio. The static stability variation ranges of the A-type shell, the B-type shell and the C-type shell are 4%~20.3%, 8.5%~23.2% and 11.4%~25.6%, respectively.