Through establishing the aeroelastic coupling analysis model,both the influence of coupling vibration between blades and tower of a wind turbine on the blade root loads and the difference degree of blade root and tower bottom loads calculated by steady and dynamic aerodynamic models are researched. To reflect the large elastic deformation and nonlinear vibration of the wind turbine,‘super-element’ model is used to discretize the blades,tower and drive shaft into into a series of rigid bodies connected with joints,springs and dampers. Then a multi-body system of the wind turbine is built. The Beddoes-Leishman(B-L) dynamic stall model is introduced to the blade element momentum(BEM) model to investigate the dynamic characteristics of aerodynamic loads. By adopting the theory of computational dynamics of multi-body system and wind turbine aerodynamic model,the aeroelastic coupling equations of the constrained wind turbine are established. A 5-MW wind turbine is chosen as the research subject. Via changing the constraint conditions,the effect of the wind rotor vibrations on the blade root aeroelastic loads is investigated. Using the steady and dynamic aerodynamic models,the dynamic coupling effect of blade root and tower bottom loads is studied by comparing the steady and dynamic aerodynamic models. The analysis indicates that the motions of of the components,such as the tower and drive shaft,have significant effects on the blade root aeroelastic loads. And the blade dynamic stall characteristics can considerably affect the blade root aeroelastic loads and fatigue loads spectrum. The research offers a foundation for the stable operation of wind turbine and fatigue life design.