Abstract: Using meteorological and environmental monitoring data, a typical environmental pollution process was diagnostic analyzed from viewpoints of temporal and spatial variation of pollutant concentration, atmospheric background field, physical field and other relevant factors from September 12 to 19 in 2008 in Haikou, Hainan.Resultsshow that the continental anticyclone ridge and Indian trough are the main synoptic situation which affects the atmospheric environmental quality in Haikou; its alternating evolution corresponds to environment process caused by pollutant concentration change from the peak and trough.Continuous downdraft caused by continental anticyclone ridge and pollutants convergence zone in boundary layer lead to pollutant accumulating to the peak; at the same time, deep downdraft caused by tropical cyclone periphery contributes to the pollutant concentration accumulating.Moreover, Indian and Burma trough, southerly winds and significant rain are conductive to clear the atmosphere pollutants.Therefore, a high pressure ridge in tropical region and the local flow convergence in Haikou are the main reasons for the pollutant accumulation to peak.