To remove Ni(Ⅱ) in wastewater more effectively and economically, soybean straw with low cost is chosen to make biochar to absorb Ni(Ⅱ). The effects of carbonization temperature, solution pH, adsorbent dosage, solution temperature and Cd(Ⅱ) concentration on the adsorption are investigated to find the optimal adsorption condition. A new method for removing heavy metal nickel is developed, and the adsorption kinetics and adsorption isotherm are studied. The experimental results show that the adsorption performance of the adsorbent is good, and when Ni (Ⅱ) concentration is 20 mg/L, carbonization temperature is 500℃, pH is 7, dosage is 0.2 g, temperature keeps at 25℃ and the concentration of Cd (Ⅱ) is 0, the adsorption condition is the best. The adsorption reaction accords with the second-order kinetics equation. The adsorption isotherm accords with Langmuir model, and the saturated adsorption capacity is 14.38 mg/L at 25℃. Scanning electron microscope analysis shows that the pore structure of straw, the surface roughness and the specific surface area increase, which improves the adsorption performance.