The Wells turbine blade with a bidirectional curved-surface design is frequently applied for hydropower and wind power generations. This study proposes a new design method to improve traditional straight-shaped blade based on the key-design points determining by curvature of the blade profile and to increase the turbine efficiency. To measure the rotating speed of the electrical generator that the new turbine driven, this study develops a simple wind-generating tube for power evaluation. Experimental turbine prototypes were manufactured by a CNC engraving device, and the optimal parametric design was derived through Taguchi's experiments. Finally, confirmation experiments were performed to verify the outcomes of the improved design. Results showed that the proposed method can enhance the turbine efficiency by 10% approximate.