Abstract: An aeroelastic analysis mathematic model of the horizontal axis wind turbine blades was brought forward using finite element method based on Hamilton’s principle. The extended transformation matrixes were introduced in this paper based on the moderate deflection beam model. 5-node 18-degree-of-freedom beam element was developed for the discretization of the blade. The Suzuki‘s dynamic inflow model and the modified Leishman-Beddoes dynamic stall model were used to calculate the unsteady aerodynamic loads. A Pre-curved coordinate frame was introduced to describe the profile of Pre-curved turbine blade. Then the wind turbine blade aeroelasticity model was built on the inertial coordinate frame and evaluated using Newmark integration method. Finally,the comparison with NREL’s unsteady aerodynamics experiment Phase VI and another 1.5MW wind turbine computation example verified the correctness of the mathematic model brought forward in this paper.