Abstract: During the recent 50 years, the average time on site of sunshine duration in Fengtai, Beijing shows a distinct descreasing tendency. The lapse rate is 146. 1 hours per 10 years and it in 2003 even reaches the standard that the United Nations set which called the abnormal weather. At the same time, the visibility restriction in Fengtai increases seriously. Two of them present negative correlation. The related coefficient is- 0. 626, passing the check of which the significance is 0. 001.The time of sunshine and the visibility restriction phenomeno have a link between them. Through the deep analysis, it showed that the real cause of tne sunshine time decreasing is the urbanization.