Abstract: In this paper, we analyzed the contents and δ34S values of total sulfur, carbon-bonded sulfur, ester-bonded sulfate, SO₄^2-, total reduced inorganic sulfur and stream SO₄^2-, and SRB quantity at different depths in calcareous soil and yellow soil profiles in Chenqi and Houzhaihe small karst catchments of Puding County in Guizhou Province, with the aim of elucidating the response of soils in karst catchments to atmospheric acid deposition. The results showed that under the same acid deposition level, there were significant differences in the sulfur content and δ34S values of different sulfur forms and SRB numbers in the calcareous soil and yellow soil profiles. Also more than 70% of the SO₄^2- in the stream water of sampled slope came from soils at different depths in calcareous soil and yellow soil profiles. These results indicate the different response of calcareous soil and yellow soil to atmospheric acid deposition. The formation of organic sulfur and dissimilatory SO₄^2- reduction are sulfur retention processes that exist in both calcareous soil and yellow soil profiles. SO₄^2- adsorption exists in the yellow soil profile and accumulates in the bottom soil layers; therefore, SO₄^2- adsorption is the main cause of sulfur retention in yellow soil. The SO42- exported from the calcareous soil and yellow soil profiles is mainly from SO₄^2- input from atmospheric acid deposition and not from organic sulfur mineralization of the soil itself. However, organic sulfur is the dominant sulfur form in calcareous soil and yellow soil, and organic sulfur mineralization in these two types of profiles may release a large amount of SO₄^2- into the surface water after the sulfur deposition flux is significantly reduced.