The aero-structural numerical model of the blade considering the three-dimensional effect is established for the NREL 5 MW wind turbine blade. Calculation results for the surface flow, aerodynamic load characteristics and structural deformation of the composite blade by two numerical simulation methods of CFD and BEM are comparatively studied. It is demonstrated that for the spar cap carbon fiber reinforced blade, the difference of the load concentration force calculated by the CFD and BEM aerodynamic models has little effect on the calculation results of the structural deformation. Compared with the traditional quarter chord-wise aerodynamic center, the pressure center of the blade considering the three-dimensional effect fluctuates in the range of 0.30-0.35 relative to the chord length from the leading edge, and different aerodynamic loading positions affect the calculation results of bending-torsional coupling angular displacement. Different from the traditional aerodynamic center, the peak point of the angular displacement curve calculated by taking the pressure center as the load action position moves forward, and the optimal laminate layout angle decreases. Therefore, the establishment of a blade aero-structural numerical model considering the three-dimensional flow effect has important guiding significance for the design and analysis of large wind turbine blades.