Savonius wind turbines are a type of vertical axis wind turbine. In this research, the effect of some design parameters such as blade type, overlap ratio, separation distance, and blade thickness on the aerodynamic performance of a two-bladed Savonius wind turbine with the rotor diameter of 0,3 m was investigated numerically by using a realizable k-epsilon turbulence model. Three different levels were selected for each parameter. Computational fluid dynamics analyses were performed using Fluent software and the Taguchi method was used for the optimization process. It was seen that a Savonius rotor with an elliptical blade that has a 2 mm thickness, a 0,15 overlap ratio, and a 7,5 mm separation distance shows the best aerodynamic performance. The difference between the aerodynamic performances of the base and the optimized rotor was found to be greater at higher tip speed ratios than at lower tip speed ratios. The power coefficient was raised by nearly 17,9% for a tip speed ratio = 0,8. The optimal tip speed ratio value was changed from 0,8 to 1,0, after the optimization process.