Acid rain is one of the global environmental problems that have become a very serious issue especially in southern China. Calcium ions are the nutrients needed by plants, the Ca2+ contents in forest soils would change greatly when influenced by acid deposition, and even limiting the growth of plants seriously. In this paper, two major forests’ soil of Dinghushan Biosphere Reserve, Monsoon evergreen broadleaf forest (MEBF) and Pine and broad-leaf mixed forest (PBMF), which located at the low subtropics of China, were selected to discuss the dynamics of exchangeable calcium ions under different acidity. It showed that in 2009, the calcium ions’ background values, (0.2918mg/L), in the MEBF are higher than that of the PBMF, (0.1345mg/L). For the two forests’ soils, the contents of exchangeable Ca2+ varied greatly with soil depth, but the MEBF ecosystem would be more stable than the PBMF.