To improve the removal efficiency of chromium in the water and obtain a kind of adsorbent with low-cost and high efficiency, corn stover biochar was produced and modified by zinc chloride(ZnCl2). The experimental results show that when the dosage of modified carbon is 2g /L, the initial pH is 2, the initial concentration of Cr( VI) is 100 mg /L and the adsorption time is 6 h，the Cr( VI) removal rate can reach 99.3% under the optimal modifier ratio, which is 73.7% higher than that of unmodified biochar. Furthermore, the effects of single factors such as modifier ratio, solution pH, adsorption temperature and ionic strength on the adsorption performance were investigated. The adsorption kinetics and adsorption isotherms of modified carbon on Cr(VI) were also studied. The results indicate that the adsorption is a spontaneous endothermic process and the adsorption reaction is in accordance with the quasi-second-order kinetic equation and the Langmiur isothermal model. The maximum saturated adsorption capacity is 72.46 mg/g. The pristine biochar(BC) and modified biochar(MBC) were characterized by SEM, XRD and FTIR. The analysis shows that the modified carbon microporous structure is obvious, the adsorption site and the degree of aromatization are increased, thereby improving the adsorption performance, and zinc is present on the surface of the biochar as hydroxide particles.