Abstract: In the paper,some case studies and statistical studies are performed on the relationship between the distribution of pH values of wet precipitation in Shanghai and horizonal air transport in the surface layer.The distribution of pH values of wet precipitation in Shanghai is closely related to the surface wind velocity, the prevailing wind direction,the maximum mixed depth (MMD) and the ventilation coefficient.In the city areas, whether or not the pH value of wet precipitation is less than 5.6 depends on the prevailing wind direction. In the leeward of the city, the pH value of wet precipitation decreases with the increase of the surface wind velocity and the ventilation coefficient.