Acid sulphate soils are the main soil types in the Thai Binh province, which play an important role for agricultural production in the province as well as in Red river delta. Under the influences of climate changes, land use and others, acid sulphate soils in Thai Binh have been changing in both area and quality. The results for these soils in Thai Binh from 1987 to 2007 showed that total area of the acid sulphate soils decreased 2,689.2 ha
of which the areas of the potential acid sulphate soil decreased 4,873.6 ha, the actual acid sulphate soil increased 2,184.5 ha. By comparing the soil analysis data from the survey in 1987 and from our survey in 2007, the quality of these soils was significant change after 20 years of using. The pH value increased in top soil layers, but it did not change in the pyrite and jarosite layers. The iron and aluminum exchangeability were decreased, especially for top soil layer. The particle sizes of sand were increased, but limo us and clay were decreased in both acid sulphate soils, because of influences of water regime. The dissolve sulphate were slightly changed in the top soil layer, but it were increased in the pyrite and jarosite layers. Depth appears of pyrite layer increased from 25 - 40 cm. Total nutrient contents such as organic matter, nitrogen, total base cation and cation exchangeable capacity were decreased in both acid sulphate soil. Total phosphorus and available phosphorus trend increased in both acid sulphate soil.