Considering flexible blade section torsion and shape change, the aeroelastic characteristic analysis of horizontal axis wind turbine was carried out. The blade was simplified as a cantilever and discretely modeled by applying two-node beam element. Then the aerodynamic behaviors of section deformations caused by flap-wise, edge-wise and twist were analyzed. Through establishing the structure dynamic equation, calculating loads on the blade, and applying Newmark method, a corresponding FEM program was developed to carry out the numerical analysis. As an example, the aerodynamic behavior of the 5 MW offshore baseline wind turbine rotor was calculated. The aerodynamic force and aerodynamic torque were obtained by the iterative process. The effect of blade section deformation on aerodynamic force and aerodynamic torque was also analyzed.