Wind turbine blade pitch angle control system can generally divided into two types : active control system and passive control system. This paper will focus on passive control system. The main concept is a metal torsion bar device. Let torsion bar connect with the axis of wind turbine blades that can make blades has torsion characteristic. When the wind speed goes up, the torsion bar will change the attack angle of blades. It would not only improve overall efficiency but also reduce the damage of blade structure. There are two parts of this research：experiment measurements and computer simulation. Experiment measurement will made by small wind tunnel equipment, the testing blade had been optimize design. Testing items are include：pitch angle changes, different wind speed, different stiffness of torsion bar and the torsion direction. In the other hand, computer simulation is using MATLAB-simulink for 2D emotional simulation and ANSYS-Workbench CFX for 3D simulation. The results of experiment, the torsion bar device could work in high wind speed situation. It not only protected blade structure but also improved about 18% efficiency. Compare to computer simulation, whether 2D dynamic simulation and 3D-CFD simulation are really fit to experimental results. To sum up, this torsion bar device is really suit for small wind turbine blades in the high wind speed situation. This research could improve the design of small wind turbine blade.