The purplish soil from the landfill in Yunxi Town， Yanting County， Sichuan Province was used to study the changes in the content of available heavy metals including Cd，Cu，Pb，Zn before and after passivation culture. Different mass ratios of silicon fertilizer （Si1：0.5%， Si2：1.0%） and phosphate ore powder （P1：0.2%， P2：0.4%， P3：1.0%） were mixed as compound and added to the soil. The passivation was cultured for 90 days. The effectiveness of soil remediation was evaluated with risk assessment code （RAC）. The results showed that the effectiveness of heavy metals under the treatment with high silicon （Si2：1.0%） was significantly reduced compared with that under the treatment with low silicon （Si1：0.5%）. Among them， Si2P3 treatment had the highest passivation rate for Cd， Cu， Pb， and Zn， which was 30.79%， 27.27%， 27.13%， and 36.88%， respectively. There was no significant difference between Si2P1 treatment and Si2P2 treatment. Si2P1 treatment significantly reduced the toxicity of heavy metal leaching and the RAC risk assessment code of heavy metals. It is indicated that the passivator for compound mainly enhanced the complex-precipitation of functional groups （O-Si-O，Si-O-Si，H₂PO₄^-，PO₄^3-， etc.） by increasing the pH and EC value in soil， promoting the transformation of heavy metals from highly active weak acid extraction and reducible states to low actively oxidizable and residual states. Overall， the application amount of Si2P1 passivator is lower， making it more suitable for the remediation of heavy metal contaminated soil in landfills.