In order to improve the aerodynamic performance of automobile, it is of importance to induce air flow to right direction reducing the drag force. Low pressure is formed at the upper surface than the bottom, which is evidence that lift occurs on most of the vehicle. In other words, the air tries to flow from the bottom of the high pressure to the side and top surface. This creates a trailing vortex in the wake, and it is clear that much energy goes to large air vortex and becomes a drag source. In this study, seven different angles of air guiding fin of C-pillar were numerically investigated to confirm the aerodynamic characteristics by using the commercial CFD code, ANSYS ver. 17.1. The numerical results of the present study and existing experimental data of the drag coefficient(CD) were compared to evaluate the reliability of the numerical method and they showed a good agreement.