In this paper, biochar was prepared from plateau livestock and poultry manure and corn straw at different temperatures, and its adsorption of cadmium in water was studied. The physicochemical properties, optimal adsorption pH value, adsorption kinetics test and adsorption isotherm test of biochar prepared at different temperatures were studied. The research results indicate that as the preparation temperature increases, the yield of biochar decreases, the ash content increases, and the pH value increases. When the pH is 8, the adsorption effect of biochar on cadmium is better. 5 h is the best adsorption time, and kinetic adsorption belongs to a quasi-secondary model, which is dominated by chemisorption. The optimal preparation temperature is 700 °C.