A pot experiment was conducted to compare the remediation effects of different soil amendments derived from crawfish shell on an arsenic (As) and lead (Pb) contaminated soil. Soil amendments, including crawfish shell powder (CSP), chitin (CT), crawfish shell biochar (CSB) and CT-CSB combination (CT-CSB, CT∶CSB is 1∶1), were employed to assess the influence of their applications (1%) on the availability of nutrients, activities of enzymes, bioavailability of As and Pb, as well as growth of pak choi (Brassica chinensis). The results indicated that all treatments significantly increased the pH and cation exchange capacity (CEC) of the soil. Concentrations of available Pb decreased in all treatments, and the maximum reduction was found in the CSB treatment, which was 35.3% lower than control. Application of CT, CSB and CT-CSB decreased the concentrations of available As, and the maximum reduction was found in the CT-CSB treatment, which was 77.2% lower than control. The activities of soil enzymes including α-glucosidase, cellobiohydrolase, xylosidase, acetyl glucosaminidase and acid phosphatase were enhanced after the addition of CT, CSB and CT-CSB. Correlations analysis between soil enzyme activity and the concentrations of available Pb and As indicated that the application of different amendments could alleviate the stress of As and Pb in the soil, and thus enhance soil enzyme activities. Application of all amendments decreased the uptake of As and Pb in the edible part of pak choi, and increased the phytoavailability of nitrogen, phosphorus and potassium, thus promoting plant growth. The biomass of the edible part of pak choi increased by 190.9% in the CT-CSB treatment, compared with the control. In conclusion, application of CT, CSB and CT-CSB, in particular CSB, had superior potential for promoting plant growth and remediating soil polluted by As and Pb, offering a new approach for the in-situ remediation of soil co-contaminated with As and Pb.