The paper analyzes systematically the air pollution situation and the causes of the fog and haze in Suining City by studying the air quality trend,variation of composition and concentration of airborne particulate matter in the city. And the horizontal comparison is also conducted among cities of Sichuan Province. The fine particulate matter (PM2.5) concentration in Suining City ranged from 35 μg·m-3 to 119 μg·m-3, and the average value is 68 μg·m-3 in 2012. While the PM2.5 concentration in Suining ranged from 21 μg·m-3 to 120 μg·m-3 from January to April in 2013,the qualification rate was below 50%. Especially in march 2013,PM2.5/PM10 decreased from 62.0%—87.2% to 45.3%. Judged by the data,the air quality in Suining City is mainly affected by pollution pattern of fine particulate matters,climate conditions and long-distance transportation of the air pollutants. And the main source of fine particulate matters is motor vehicle exhaust. The countermeasures to prevent and control particulate matter pollution were put forward accordingly for the city.