Abstract: Biochar was prepared by high-temperature pyrolysis with bulk agricultural waste corn straws as raw material, and the performance of biochar on heavy metal removal was investigated through the adsorption experiments of lead and cadmium in water.The results showed that the corn straw biochar obtained at 800 ℃ was mainly in the form of block and rod, the pore structure was micropores, and the alkali metals and alkaline earth metals in the ash were dominated. The maximum adsorption capacities of Pb²⁺ and Cd²⁺ were 94.79 and 24.47 mg/g, respectively, when the adsorption temperature was 25 ℃, pH value was 4, adsorption time was 960 min, and the mass concentrations of Pb²⁺ and Cd²⁺ were 429.24 and 280.34 mg/L. The removal process of lead and cadmium in water by biochar followed the pseudo-second-order kinetic equation and the Freundlich isotherm model. When the initial mass concentrations of lead and cadmium were all 150 mg/L, the obtained equilibrium adsorption capacities were 69.0 and 24.4 mg/g, respectively. Thermodynamic analysis showed that the process belongs to endothermic and entropy increasing. Additionally, Pb²⁺ could significantly antagonize the removal of Cd²⁺ in binary metal ion solution.The adsorption mechanism of corn straw biochar indicated that the removal of both metal ions was the combination of physical adsorption and chemical precipitation.