In order to clarify the response of soil structural distribution and Cd fugacity to zero-valent iron nanoparticles-chitosan modified biochar，this study was conducted to investigate the effects of 1%-3% modified biochar input treatment on soil pH，organic carbon(SOC)，cationic exchange capacity(CEC)，water-stable agglomerates and different Cd forms under different concentrations of CdCl2 solution contamination conditions. The results showed that after 300 d of sedimentation，the soil pH，CEC and SOC were increased significantly by 8.30%，17.23% and 68.48%，respectively，compared with those of the CK. The content of large agglomerates(> 0.25 mm)was increased by 7.69%，and the effective Cd content was decreased in the weakly acid-extracted，reducible and oxidizable states. The effective Cd content were decreased by 12.61%，5.52% and 1.21%，respectively，and the ineffective Cd content(residual state)was increased by 19.34%. The path analysis showed that soil pH and SOC content directly affected the content of effective Cd and there was a causal relationship between the content of SOC and the formation of soil small particle agglomerates(< 0.25 mm)，and there was a causal relationship between the formation of soil small particle agglomerates and CEC content and effective Cd. From the results of the pathway analysis，soil CEC and soil agglomerates were the key role factors of soil Cd effectiveness. Under the present experimental conditions，the zero-valent iron nanoparticle-chitosan modified biochar was more effective on Cd fixation for soil with high Cd concentration.