Corn straw biochar prepared under 400 °C was the best Cd and Pb adsorption capacity Maximum adsorption capacity of Cd and Pb were 43.48 and 22.73 mg·g , respectively The dominant mechanism of Cd and Pb adsorption was precipitation Biochar could reduce the bioavailability of heavy metals when mixed with soil Cadmium (Cd) and lead (Pb) in water and soil could be adsorbed by biochar produced from corn straw. Biochar pyrolyzed under 400°C for 2 h could reach the ideal removal efficiencies (99.24% and 98.62% for Cd and Pb, respectively) from water with the biochar dosage of 20 g·L and initial concentration of 20 mg·L . The pH value of 4–7 was the optimal range for adsorption reaction. The adsorption mechanism was discussed on the basis of a range of characterizations, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Raman analysis; it was concluded as surface complexation with active sorption sites (-OH, -COO-), coordination with π electrons (C= C, C= O) and precipitation with inorganic anions (OH , CO , SO ) for both Cd and Pb. The sorption isotherms fit Langmuir model rather than Freundlich model, and the saturated sorption capacities for Cd and Pb were 38.91 mg·g and 28.99 mg·g , respectively. When mixed with soil, biochar could effectively increase alkalinity and reduce bioavailability of heavy metals. Thus, biochar derived from corn straw would be a green material for both removal of heavy metals and amelioration of soil.