An iterative simulation on wind field and rain field in one three-tower connected tall buildings in southeast coastal region in China was carried out based on the computational fluid dynamic technology. In the iterative simulation， the wind-rain two-way coupled algorithm was viewed as the core and the continuous phase model and discrete phase model were used. Firstly， the nonsteady fluctuating wind fields in connected buildings were simulated under 9 wind-rain working conditions. The average wind pressure distribution， the surface velocity streamline， and the flow field disturbance mechanism of the three-tower connected tall buildings were discussed. Secondly， the number of raindrops on the principal tower surface， impact force of raindrops， and distribution law of rain pressure coefficient at different wind-rain working conditions were compared. The structural surface velocity streamline， raindrop travelling path and action mechanism of the final velocity in the wind-rain coupled field were disclosed. Finally， the most unfavorable wind-rain working condition for the three-tower connected tall buildings was recognized. The recommended values of the rain pressure coefficient were given. The results demonstrated that the rain load on the windward surface of the three-tower connected tall buildings in the wind-rain coupled environment was the most significant. The maximum rain-to-wind load ratio reached 23.81% and the maximum rain pressure coefficient at local measuring points reached 0.301. The wind velocity and strong rainstorm combination was the most unfavorable wind-rain working condition in the 100-year recurrence interval.