Abstract:From analysis of the data of air contaminant density monitored by Yinchuan Envir omental Monitor Station during 5 years (1997~2002) and of the weather chart,the conclusion can be drawn that the serious air pollution mainly occurred in the w inter days.The main contaminants are TSP and SO2.From October to the next Janu ary,the situation that density of TSP exceeds the standard point happens more fr equently than that of SO2,while from the February to June,the opposite case is true. The main weather situations that influence the concentration of contaminants are mainly the following:the northwestward air current,the eastward cold air current traversing the air ridge,the eastward cold air trough,air current along the lat itude and southeastward air current.The analysis of the weather situation betwee n Oct,2001 and Dec,2002 and the result of CAPPS Numerical Prediction System show that,the possibility of failure to report density of SO2 exceeing the stand ard point may reduce 20 %. As for as PM10 is concerned,the reduction is 18 %.