In this paper,a simple method for simultaneous determination of exchangeable acidity and exchangeable alkalinity of soils which could distinguish to Na-exchangeable acidity,Ba-exchaogeable acidity,SO₄-exchangeable alkalinity and F-exchangeable alkalinity was proposed.The exchangeable acidity and exchangeable alkalinity of various red soils derived from different parent materials in South China were determined with the proposed method in the field.The results showed that acid red soils contained not only large amount of exchangeable acid but also considerable quantities of exchangeable alkali.Because Ba²⁺ ions possess a stronger power than Na⁺ ions in replacing exchangeable aluminium ions,which are the principal cause of soil acidity,the amount of Ba-exchangeable acid was larger than that of Na-exchangeable acid.Likewise,because the amount of OH^- ions released by ligand exchange between F^- ions and hydroxyl groups on the surface of soil particles was higher than that when SO₄^2- ions were used,the amount of F-exchangeable alkali was larger than that of SO₄-exchangeable alkali.For the same type of soil,the amounts of exchangeable alkali of red soils derived from acid parent materials were higher than that of the soils derived from basic rocks.The amounts of exchangeable acidity and exchangeable alkalinity increased with the increase in neutral salt concentration up to 0.1 N,and then approached a constant value.