Abstract: Air pollution of Urumqi is a very serious issue，especially in winter due to the high emissions from residential heating. In past decades，the concentration of SO2 was increased rapidly，which becomes an environmental problem that can not be ignored. Although the Government has taken a series of measures such as desulfurization，the increasing coal consumption leads to the concentration of SO₂ remaining high，which still seriously impacts the quality of atmospheric environment. In order to improve the serious air pollution in winter thoroughly，the local government has implemented energy structure adjustment work，the “coal to gas” project. Whether the project played a decisive role to control concentration of SO2? The aim of this paper is to investigate the situation of the most serious pollution period of winter （1-2 months） in 2009 and 2013，and analyze the change of daily average of SO2 concentration before and after "coal to gas" in different areas of the city. The daily average of SO2 concentration data were analyzed by using Thermo Scientific TEOM 1405-F continuous monitor. The results show that after the project the daily average of SO2 concentration decreases obviously，but the declines are differences in the different regions. Before project “coal to gas”，the daily average of SO2 concentration generally exceeded the States Concentration Limit Class 2 Standard （0.15 mg·m^-3）. In southern and middle areas of city，the SO2 exceeded the rates from 25 to 40% in different areas of the whole city. After the project，from the south to the north，the daily average of SO2 concentration increased gradually in winter. Substituting coal by gas would reduce SO2 emissions by 65.9%，69.6% and 48.8%，respectively. In the south and middle areas，the daily average of SO₂ concentration can reach the States Concentration Limit Class 2 Standard；in the north area，the concentration of SO₂ was decreased，but it was often higher than that of the States Concentration Limit Class 2 Standard. The south and middle areas’ monitoring points are located at relatively high altitudes，pollution sources are relatively less，and the pollutants are easy to be  spread；in the north area，the monitoring point has lower altitude，the pollutants are difficult to be diffused，moreover a large number of civilian boiler emissions and the effect of the urban hot island，all of them can easily cause serious air pollution in the urban fringe，the local government is worth paying much attention to the environmental management.

Key words: coal to gas, patial distribution, ir pollution, oncentration change