Abstract: Abstract：The column leaching and batch incubation experiments were conducted to investigate the effect of nano-hydroxyapatite addition on the bioaccessibility and speciation of Cd and Zn in yellow soil in pyrite areas.Additive ratios of nano-hydroxyapatite were set as 0% (CK), 1% (weight ratio, P1), 3% (P3) and 5% (P5).It was found that: (1) Nano-hydroxyapatite could increase pH of the leachate and decrease leaching loss of Cd and Zn significantly.Compared with the CK (leaching loss of Cd and Zn were 120 μg and 16.7 mg, respectively), Cd and Zn accumulated leaching in P1, P3 and P5 declined by 74.2%, 85.0%, 92.0% and 79.4%, 92.1%, 97.9% correspondingly; (2) Nano-hydroxyapatite could increase soil pH remarkedly, and the soil pH increased by 0.64, 0.85 and 1.20 of pH units in P1, P3 and P5 treatments after 45 days incubation; (3) In comparison with the CK, nano-hydroxyapatite addition at P1, P3 and P5 reduced available Cd and Zn determined by 0.025 M HCl extraction by 74.2%, 96.8%, 98.4% and 68.1%, 96.6%, 99.5% respectively; (4) Nano-hydroxyapatite significantly decreased the concentrations of exchangeable and carbonate bounded Cd and Zn in sequential extraction, and increased residual fractions, which promoted the transformation of Cd and Zn from the active forms to the inactive ones in the soil.These findings indicated that nano-hydroxyapatite could effectively decrease the heavy metals risk in the soil and had good applications prospect in the remediation of Cd and Zn contaminated soil in typical pyrite regions of Southwest China.