The yearly averaged sunshine duration,cloud cover,surface vapor pressure and visibility from four meteorological stations(the urban area,Xiqing,Jixian and Tanggu) in Tianjin are analyzed.The results show that the sunshine duration decreased significantly for the past 40 years at the four stations;the variation rates of the annual sunshine duration are-177.3,-165.2,-174.1 and-145.6 hours per ten years,respectively;compared to the 1960s,the mean annual sunshine durations decreased by 425.1,403.4,486.0,and 377.5 hours in the 1990s,which is equivalent to a decrease of 1.2,1.1,1.3,and 1.0 hours in daily sunshine duration for the four stations;there is no long-term variation trend in cloud cover and surface vapor pressure for the four stations,but surface visibility witnessed a tremendous drop in the analyzed period.It indicates that the principal cause for the sunshine duration variation is the decrease of surface visibility resulted from the increase of atmospheric aerosol concentration due to the rapid development of the local industries and economy.