The effects of different modifiers, such as potassium dihydrogen phosphate, calcium carbonate, sodium silicate, homemade plant ash and homemade biochar on immobilization in copper contaminated soil were investigated respectively, and the immobilization mechanism was clarified through analyzing heavy metal fractions by using modified European Community Bureau of Reference (BCR) method and X–ray diffraction (XRD). The results showed that the best dosing quantity (mass ratio) of the five modifiers was 50, 100, 20, 20, and 20 g/kg, respectively, and the amount of soluble Cu in soils decreased and residual Cu increased rapidly when modifiers were added in soils. Among them the plant ash made by ourselves which improved soil pH and generated precipitation with Cu was most effective to reduce Cu availability, the use of plant ash reduced the amounts of available and soluble Cu about 53% and 49.2% respectively, while increased residual Cu about 4.7 times of the original soils.