In order to distinguish whether thermal mechanism or ionization mechanism dominates shock wave control process by plasma aerodynamic actuation, the transformation rules of wedge oblique shock wave control by arc discharge plasma were theoretically deduced using thermal choking model and ionic sound wave model respectively. If the thermal mechanism dominates shock wave control process, the shock wave start point will shift upward, its shape will not bend and its angle will decrease. However, if the ionization mechanism dominates shock wave control process, the shock wave start point will maintain at the wedge forward apex, its shape will bend as two subsections and its angle of first subsection will increase. Then the wedge oblique shock wave control by arc discharge plasma was studied in a small-scale short-duration supersonic wind tunnel, and the test results showed that the shock wave start point shifted upward 4 mm, its angle decreased 8.6% and its shape did not bend, which demonstrated that the thermal mechanism dominated the shock wave control process by plasma aerodynamic actuation.