Abstract: Shanghai is the largest industrial and commercial city in China.The urban turbidity island effect is remarkable. 1) The comparison of air quality between urban and rural areas shows that the concentration of urban air pollutants such as SO₂,NO_x,fly ash and falling dust is much higher than that of rural air pollutants. 2) Due to the more hygroscopic nuclei in the urban atmosphere and the thermal turbulence and mechanical turbulence in urban area are stronger, the low cloud amount in urban area is greater than that in rural areas. 3) Taking the ratio of solar direct radiation(S) to diffuse radiation(D) as the measure ofturbidity factor(D/S),it can be seen that the turbidity factor in urban area is obviously greater than that of suburban area.The urban district as a center,a distinct turbidity island is formed.This kind of turbidity island effect is gradually increasing with the development of Shanghai city.