Abstract: A three-dimensional mesoscale Monte-Carlo model in which orographic influence,vertical asymllletry of turbulent statistic and non-equilibrium effect are considered has been used to study the sPatial and temPoral distribution of atmosPheric SO2 concentration in ZHUHAI region.The results show the daily concentration variation under mountain-valley-breeze and land-sea-breeze controlling The average rate of computational and observational concentration is 0.94+0.2388,that is satisfied.The model has advantage of clear concept,no special artificial assumption and no pseudo-diffusion,and can better reveal the random characteristic which turbulent diffusion involve itself.