To investigate the changes in pH and potential influencing acidification indicators at different depths of red soil under different vegetations is significant for preventing soil acidification and improving soil quality. A series of soil samples were collected at depths of 0-20, 20-40, 40-60, 60-80 and 80-100 cm across two sites (Qiyang County of Hunan Province and Yujiang County of Jiangxi Province) from Quaternary red earth under two land use types (paddy field, dry land). Soil pH, organic matter, exchangeable base cation and exchangeable aluminum were determined, and their inner relationship was analyzed. The results show that pH of red soil profiles from Quaternary red earth is below 6.50, and increases with the increase of soil depth at 0-100 cm. Under different land use types, pH follows the order of paddy field (5.80-6.43)> dry land (4.68-5.41), the concentration of soil exchangeable aluminum follows the order of dry land (4.22-7.02) > paddy field (0.16-1.56), and it decreases with the increase of soil depth at 0-100 cm under paddy field, while dry land shows the opposite tendency. Soil exchangeable aluminum is negatively correlated with soil organic matter at 0-20 cm layer, and negatively correlated with soil exchangeable base cation at 40-100 cm layer. This study indicates that land use type is one of the important factors influencing soil acidity, and dry land has stronger acidity than paddy field. Increasing organic matter in 0-20 cm may be one of the measures to slow down acidification and reduce soil exchangeable aluminum.