Purpose <p>During the operation of large wind turbines, the blade vibration is a problem that needs to be avoided. Modern large-scale wind turbines use variable pitch technology to adapt to different working environments, but it can exacerbate blade vibration problems. In this paper, the influences of the rigid pitch motion on the coupled flapwise-edgewise bending vibration characteristics of a wind turbine blade are studied.</p> Methods <p>The blade is simplified as a rotating cantilever beam with inherent rigid-flexible coupled vibration. Based on the Euler–Bernoulli beam theory and the Hamiltonian principle, the nonlinear dynamic equation of the coupled flapwise-edgewise bending vibration of the rotating pitching blade is established, where the harmonic pitch motion is considered and the unsteady aerodynamic forces based on the Greenberg empirical formula are employed. The control equations of static displacement and dynamic displacement are obtained by applying the modal superposition method and displacement decomposition. The nonlinear dynamic responses of blade with harmonic pitch motion are analyzed by employing direct numerical integration method.</p> Results <p>It is concluded that the system is sensitive to the parameter B. When it is a rational number, there is a multi-period response. When it is an irrational number, there is a quasi-periodic response. In the flapwise direction, there are two ranges of the resonance interval for the parameter B. One is from 0 to 1, and the other is from 10 to 12. But in the edgewise direction, it is from 10 to 12.</p> Conclusions <p>The proposed method helps to understand the blade vibration characteristics during the pitch control process. It is effective for the blade vibration. Avoiding the dangerous values of the pitch control system, we can ensure the safe operation of the wind turbine.</p>