Abstract: The adsorption behavior of red gypsum（RG） to cadmium was studied by isothermal adsorption method and the neutralization ability of RG to soil was determined.Then the change of effective Cd content in the Cd-contaminated soils with adding RG as soil ameliorant was researched.The Langmuir model was found to describe well the adsorption process，where maximum adsorption capacity was 18.29 mg/g at pH of 6.The adsorption capacity increased with the increase of pH.The acid and basic neutralization capacity tests of RG showed that the addition of RG to the soils could increase the soil pH and its sta- bility，thus decreased Cd-bioavailability.The application of RG was found to significantly reduce the MgCl₂，DTPA and HCl extractable Cd concentrations in soil，the highest decreases were 39%，33%，and 17% respectively.The leaching toxicity and heavy metal concentrations of RG were also studied，and it had no hazards to soil and groundwater.Comprehensively consider- ing the inhibition of Cd-contamination and fertilizing effect itself，RG could be an effective，feasible and environmental addi- tive for the remediation of cadmium in soil.

Key words: red gypsum, Cd pollution, ameliorant, feasibility