Cadmium (Cd) is an important heavy metal pollutant in farmland soils due to various anthropogenic activities, such as utilization of chemical fertilizers, wastewater irrigation, and sewage sludge, large areas of cultivated soils worldwide have been contaminated by Cd, in the past decades. Cd inhibits physiological processes and normal growth and reduces the biomass and yield of plants. Therefore, it is of great urgency to explore new ways for reducing the Cd content in the cultivated soils. The results from few existing studies on the effects of sulfate supply on Cd availability in soil are conflicting. In order to investigate the effect of sulfate on the migration and transformation of cadmium（Cd）in soil system, sufficient sulfate were applied to the two levels exogenous Cd-contaminated soil, soil solution was collected during four months soil culture test, and measuring pH, conductivity, cadmium content and other indicators of soil solution. The effect of sulfate on the mobility and bioavailability of Cd was examined.

The results showed that flooded environment played an important role in affecting the mobility of Cd in soil solution, the availability of cadmium in the soil increased firstly and then decreased. Long-term flooding could increase the pH of the soil and reduce the conductivity of the soil. The content of cadmium in alkaline soil was generally lower than that in acid soil during the first three months, and the content of cadmium in acid soil after flooding and adding sulfate is effectively reduced to the same level as alkaline soil at the fourth month. The addition of sulfate reduced the availability of cadmium in alkaline soil, which is on the contrary in acid soils. After comparison, flooding conditions played a greater role in reducing the cadmium content in soil solution than the addition of sulfate. The mechanism behind these phenomena needs to be further explored.