Abstract: An indoor soil culture experiment was conducted to study the effect of water regulation on the passivation of heavy metals. The results showed that: soil pH could be significantly improved and the content of available Cu and Cd in soil could be significantly reduced after adding the passivation material DLS; the bioavailability of Cd was not obviously influenced by the soil moisture content, but the soil pH and the bioavailability of Cu could be significantly affected by the soil moisture content; after the indoor culture experiment was conducted for 6 days, the highest pH appeared with the treatment of soil moisture content being 40% of the maximum field water holding capacity, and the treatment of 20% was the minimum, however, the bioavailability of Cu was contrary to the soil pH, the bioavailability of Cu was shown as the treatment of soil moisture content was 40%＜80%＜60%＜100%＜20%. In the course of field planting, the suitable soil moisture content range for plant growth was generally 40%-60%, therefore, in the process of field remediation of heavy metal contaminated soil, the soil moisture content should be kept in 40%-60% of the maximum field water holding capacity, in order to achieve the best passivation effect of the alkaline passivation material.