Abstract: In order to investigate the stabilization effect of biochar materials and the migration and transformation characteristics of co-existing heavy metals in contaminated soil, corn straw and wheat stalk were used as the raw materials in this study. Two types of biochar were prepared by anaerobic pyrolysis at 600 ℃ after loading with phosphate, and used in stabilization batch experiments in heavy metal contaminated soils. The study indicated that phosphate-loaded corn straw and wheat stalk biochar promoted the sorption of Cd by increasing the content of amorphous iron and aluminum oxides in soil. The increase of amorphous oxides and the decrease of free oxides in soil treated with corn straw biochar were higher than that of in wheat stalk biochar treated soil. Meanwhile, these two biochar materials significantly increased the iron activation and effectively control the bioavailability of heavy metals in the multi-contaminated soil. The addition of different proportions of corn and wheat phosphate-loaded biochar, such as 5%, 10% and 15%, can reduce the migration risk of Pb, Cd, Zn and Cu in soil, and promote the transformation of acid extractable fraction and Fe-Mn oxide bound fraction of Pb to organic-bound fraction and residual fraction, as well as the transformation of acid extractable fraction of Cd, Zn, and Cu to residual fraction. The two biochar materials greatly decreased the leaching concentration of heave metals, and the application of 10% or 15% can reduce the leaching concentration of Pb by more than 98%. The addition of 15% phosphate-loaded corn straw can reduce the leaching concentration of Cd by 89%, while the leaching concentration of Zn decreased by 47%, respectively. However, phosphate-loaded wheat stalk biochar with 15% addition reduced the leaching concentration of Cu by 55%. The results have shown that the application of 10%-15% phosphate-loaded biochar materials can significantly reduce the potential environmental risks of Pb and Cd in heavy metal contaminated soils, which has practical reference and guiding significance for the risk control of heavy metal contaminated soil in mining areas.