The current wind resistance design methods for cooling towers ignore the effects of rainfall. But under extreme weather conditions with strong wind along with rainstorm, the rainstorm affects aerodynamic force on internal and external surfaces directly, and change turbulent effect of fluctuating wind. However, most traditional researches pay attention to shock effect on structure surface from wind driven rain. To solve this problem, aiming at a domestic large cooling tower which had built of the world's tallest (220 m), the wind-rain two-way bidirectional coupling algorithm is as the core. Firstly， the wind field around the cooling tower is simulated based on computational fluid dynamics (CFD) method, and the pressure distribution of cooling tower is compared with national standard and existing testing curve to verify the effectiveness of the numerical simulation. And the discrete phase model (DPM) is added and the iterative computation of raindrops and wind fields is carried out. Secondly, the influence laws on wind-driven rainfall, raindrop additional force and wind-induced pressure coefficient on internal and external surface of tower drum are studied systematically, and the action mechanism of wind speed streamline, turbulence intensity and rain drops moving speed and trajectory on tower drum surface are revealed. Finally, the new model and distribution characteristics of wind-rain equivalent pressure coefficient are presented based on the wind-rain two-way bidirectional coupling algorithm. The conclusions can provide the reference for surface load value of such cooling towers.