There are about 67000ha of acid sulfate soils in China.They art mainly distrihuted in the coastal region of the southern part of China.This study deals with the amount of some acid forms in acid sulfate soils and their interrelations.Acid sulfate soils contain a large amount of pyrite,Which is a kind of potential acid form and can produce active acidity after its oxidation.The soils contain a large amount of exchange and hydrolytic acidity,generally 0.2-10.5 cmol/kg,and have a very low pH value,generally betwrrn 3.2 and 5.5.Pyrite (FeSa) is a determinant form of acidity in the soil,but the different forms of acidity are related each other in a equilibrium system.