Abstract: The measurements and analysis of pH value and chemical composition of snow and cloudwater were carried out during winters from 1982 to 1984 in Wulumuqi region of China. It shows that the mean pH value of snow is about 5.7, the pH value of cloudwater is about 4.0, with that simultaneously the observed pH value of surface snow is about 6.0. The ion concentration of liquid water in lowercloud generated within air mass is larger than that of cloud with precipitation made by synoptic systems about two orders of magnitude. A possible influence of microphysical processes of snow growth and the characteristics of aerosol particles scavenged by snow crystals on the acidity of snow is noticed