Abstract: water vapor of small droplets from natural draft cooling tower installations would contain water treatment chemicals such that contact with plants,building surfaces and human activity would be hazardous.Prediction of small droplets deposition is generally important.The relevant validation of the flow field near the Chalk point power plant cooling tower as well as its water vapor uplift and diffuse law are carried out which apply the combination of k-ε（RNG） turbulence model and Lagrangian discrete phase model（DPM） of a computational fluid dynamics（CFD） code STAR-CD,and compared with the predicted results of water vapor uplift and diffuse law of cooling tower which is used of SACTI model and Meroney’s calculated results using CFD method in this paper.Based on the validation results,the author take the related research on the impact of the water vapor diffusion respectively of different ambient wind speeds;ambient temperatures;ambient humidity and temperatures on the water vapor emissions from cooling tower.The results show that,ambient wind speed and ambient temperature have a lager impact on the cooling tower's water vapor diffusion,ambient humidity’s impact followed,and the temperature on the water vapor emissions from cooling tower is less affected.Furthermore,with the increases of ambient wind speed and ambient temperature,the concentration of water vapor ground deposition of cooling tower decreases;with the increases of ambient humidity,the concentration of water vapor ground deposition of cooling tower also increases;with the increase of temperature on the water vapor emissions from cooling tower,the concentration of water vapor ground deposition of cooling tower decrease slightly.