Abstract: By using experiments and acid base balance calculation, acid and base characteristics of ambient aerosols in Qingdao area was studied. The content of sulfuric acid in ambient aerosols was analyzed, the existing forms of Ca²⁺ and Mg²⁺ in ambient aerosols were deduced, the sources of SO^2-₄ and NO^-₃ and the contribution of IP and TSP to rainwater acidification were estimated. It is found that the total effect of IP and TSP to rainwater is neutralization function, and their neutralization capability (carbonate) is about (22±20)% of the content of Ca and Mg in ambient aerosols.