In order to study the application effect of only biochar and biochar combined with zinc on the remediation of cadmium (Cd)-contaminated soils, Cd-contaminated soil was collected from sewage irrigation area and used to cultivate wheat in a pot experiment. Combined with wheat growth parameters, antioxidant enzyme activities, and related gene expression, the soil Cd fraction and accumulation in wheat were studied under the Cd stress with the only wheat-stem biochar application at the rate of 0, 1.0%, 1.5%, and 2.0%. Besides only biochar application, combined application of zinc (Zn) with 30 mg/kg Zn sulfate heptahydrate was applied to the above four treatments. The results showed that biochar application can promote the soil exchange and carbonate-bounded Cd fraction transformation to organic-bounded and residual fractions, and the transformation rate increased with the increase of the amount of added. However, Zn application had no impact on the soil Cd fraction. The application of 1%-2% biochar significantly reduced grain Cd concentration by 29%-57%, and the grain Cd concentration was reduced to 0.1 mg/kg by the application of 2%. The grain Cd concentration was reduced by 21%-39% by only biochar application. Soil zinc and biochar application had a synergistic effect. The application of biochar and zinc can promote plant growth, improve wheat yield, and improve the antioxidant capacity of wheat root cells by regulating the activities of MDA and antioxidant enzymes (SOD, POD and CAT). The application can also regulate the expression of Cd transporter genes (TANRAMP5, TALCT1, TAHMA3 and TAHMA2) to reduce the soil Cd uptake and transport root Cd to the above ground parts, thus reducing the uptake and accumulation of Cd in wheat plants. Therefore, soil application of biochar and zinc has practical reference and guiding significance for the safe production of wheat in wastewater irrigation areas.