To study the chemical composition characteristics of dry deposition is very important to the understanding of their influence on forest ecosystem. They are the key factors to grasp the formation, transportation and deposition mechanisms of the acidic matters in the air and the aerosol. This paper studied the chemical composition characteristics of air and aerosol based on the monitor data of three typical acidic catchments, including Cai Jia Tang (CJT) in Hunan, Lei Gong Shan (LGS) in Guizhou and Tie Shan Ping (TSP) in Chongqing. The research results have indicated that the dominant acidic materials are SO2,SO42-,and NO2, and the dominant basic ones are NH+4，Ca2+，K+ and NH3. The dry deposition ratio of SO2 has a close relationship with the local sources of sulfur (S) and has seasonal variations as well. The mean seasonal concentration of (NH3+NH+4)-N is higher than (HNO3+NO-3)-N in all of the three areas. The order of annual mean concentration of NO2-N and NH3-N in the three sections are TSP>CJT>LGS. Furthermore, the gas/particle ratio for the ammonia compounds is less than 1∶1 in the three areas, and that for the nitrogen compounds is close to 1∶1 at CJT, more than 1∶1 at LGS, and less than 1∶1 in TSP.