Savonius Vertical Axis Wind Turbine (VAWT) is a type of rotating equipment that can convert wind kinetic energy into electrical energy. The advantages of this type of wind turbine are a simpler design than horizontal axis (HAWT) type wind turbines and a good ability to utilize wind from all directions. This research was conducted to obtain the optimal design of the Bach-type Savonius VAWT blade profile, especially in the blade arc angle (θ) and blade shape ratio (p/q) parameters. The method used is a two-dimensional Computational Fluid Dynamics (CFD) numerical simulation using ANSYS Fluent software and k-ε realizable turbulence models. The simulation was carried out with a flow velocity (U) of 4 m/s. The study was conducted by analyzing the aerodynamic performance of twenty-four Savonius VAWT models with variations in blade arc angle (θ) dimensions of 125°, 135°, 145°, 155°, 165° and 180° and blade shape ratio (p/q) variations of 0, 0.2, 0.4 and 0.6. The simulation coefficient of power (CoP) data will then be plotted into graphs on three- dimensional cartesian axes and contour graphs using the cubic spline interpolation method. From the formed graph found the optimal point of the turbine blade profile. The optimal design is compared back to the conventional semi-circular Savonius VAWT design to determine the improved performance of the optimized turbine. The optimal design is a model with blade arc angle (θ) = 139° and blade shape ratio (p/q) = 0.6. The optimal design yields a coefficient of momen (CoM) value of 0.277 and a CoP of 0.1943. The optimal design has an aerodynamic performance (CoP) higher by 8.78% compared to conventional designs.