With the development of the aviation industry and economic growth, business jets have become popular among business people and the public due to their advantages in comfort, convenience and time flexibility. With the tail-suspended layout, the engines are located far away from the wings can provide clean wings, fuselage closer to the ground and other benefits, but the contraction and expansion channels formed by the after-body, nacelle, and pylon cause distortion and separation through the passage, which brings additional drags. This paper investigates the parameters of tail-mounted pylon effects on aircraft aerodynamic characteristics and performances through numerical simulation. Qualitative and quantitative comparisons between different configurations are conducted and the drag, lift and pressure distribution is obtained. The mechanism of interference effects is also analyzed. The results of this study can provide guidance and help in the design of tail-mounted pylons.