This study was numerically investigated the 2D Ahmed body in slant angle of 25 degree with synthetic jet by examined the contrast between the baseline model (without jet) and active flow model, discrepancy between the 2D and 3D model, effect of Reynolds number, effect of jet location and also effect of multi-slot model on slant surface. Hence, the study and further development of active flow control such as synthetic jet which compatible with Ahmed body is a prominent technique to against the issue and enhance the capability in transportation sector. In this thesis report, improving of energy efficiency of road vehicle was addressed and investigated of the aerodynamic drag reducing techniques was conducted.