The position of the blades in a strong wind-off state will significantly affect the flow around wind turbine towers and stability of them. Especially in the extreme weather conditions of sandstorms，the adhesion of sand will also affect the turbulence characteristics of the wind and generate additional impact force on the tower. The existing researches lack the exploration of wind-sand coupling effect to explore the aerodynamic performance and structural response of large-scale wind turbines. Taking the 5 MW horizontal-axis wind turbine system independently developed by Nanjing University of Aeronautics and Astronautics as the object and wind-sand-wave two-way coupling algorithm as the core，the simultaneous iterative simulation of the typical wind field and sand combination is performed on the continuous phase and discrete phase model respectively by CFD technology. Considering the eight stop positions in a single rotation cycle of the blade，the equivalent pressure coefficient and the aerodynamic load distribution characteristics are compared and analyzed. Then combined with the finite element method，the dynamic characteristics，wind-sand induced structural response and buckling stability of the wind turbine system at different stopping positions are discussed. The results show that the load effect of sand particles on the windward surface of wind turbine tower is the most significant under the wind-sand coupling environment. The pressure coefficient of sand in some regions can reach 0.55，and the ratio of sand impact load to wind load can reach 23.7%. The wind load under different stand positions plays a dominant role in the response of the tower structure，but the effect of sand impact on the bottom of the tower cannot be ignored.