Abstract: Objective To improve the effect of straw biochars on cadmium (Cd) contaminated soil and reduce the cost, the biochars’ complexes were applied based on a pot experiment of Chinese cabbage in this study. Method The combinations of straw biochars (soybean straw biochar (SSB), rape straw biochar (RSB)) and animal slaughter waste biochar (SWB) were applied with two concentration gradients of 2.22 g kg⁻¹ (B1) and 4.44 g kg⁻¹ (B2) in order to investigate the influence of Cd fraction in the in-situ contaminated soil and Cd absorption by the Chinese cabbage. Result The results showed that compared with the control (CK), biochar application treatments significantly decreased the Cd contents in root and the aboveground part of Chinese cabbage. Under the biochar application level of 4.44 g kg⁻¹, Cd contents in roots of Chinese cabbage under the SSB2 and RSB2 treatments were significantly decreased by 33.40% and 20.49% compared with the SWB2 treatment, respectively. The bioconcentration factors of Cd in root treated with SSB2 were significantly decreased by 31.68% compared with the SWB2 treatment. In the biochar combination treatments, compared with the SSB2 treatment, Cd contents in roots and aboveground part of Chinese cabbage with the combined treatment of SSB and SWB (SSWB2) were significantly reduced by 22.57% and 36.14%, respectively. Biochar significantly reduced the bioavailability of Cd in soil. Compared with the SWB2 treatment, the proportions of exchangeable Cd (F2) in the RSB2 and SSB2 treatments decreased by 9.31% and 3.63%, respectively, while those of strongly organic bound Cd (F6) increased by 16.11% and 9.74%, respectively. Compared with the SSB2 treatment, the F2 fractionation of Cd in the SSWB2 treatment decreased by 11.05%, while the F5 fractionation of Cd increased by 13.50%. Conclusion Therefore, the combination of straw biochar and slaughter waste biochar could effectively reduce the bioavailability of Cd in contaminated soil and the Cd absorption by Chinese cabbage.