In order to study the frequency capture characteristic of wind turbine blade, a wind blade fatigue loading system with an unbalanced rotating shaft was established. With the Lagrange principle, the kinetic model was deduced and the coupling mathematical model was given. The simulation models fully explained the frequency capture process, and revealed the vibration self-synchronous properties. A series of wind blade fatigue loading trials proved that when the drive frequency was 0.48～0.58 Hz ,frequency capture phenomenon would carry out, not only the pendulum would happen, but also the wind turbine blade. When the drive frequency was out of 0.43 ～ 0.65 Hz , frequency capture phenomenon would not carry out and it would fluctuate obviously, and the more far away of the frequency capture points, the more obviously the wind turbine blade frequency and amplitude fluctuated.
