Heavy metal pollution is one of the important parts of environmental problems. In order to find out the biological adsorbent for the purification effect of heavy metal ions in water, the microwave irradiation, as well as the immersion in HCl, NaOH and NaCl, was used to modify corncob respectively. The experiment used method of control variables, and the modified corncob adsorption rate of Zn 2+ was the reference index. According to the results, the best modified condition was as follows: The power of microwave irradiation was 280 W, the time of microwave irradiation was 5 min, and the concentration of sodium chloride solutions was 0.3%. And the best adsorption condition was as follows: the diameter of corncob was about 1.5 mm, the dosage was 20 g/L, the adsorption time was 30 min, the shaking speed was 180 r/min, and the pH value of liquor zinc chloride was about 6. The results showed that modified corncob adsorption rate of Zn 2+ was more than 90% at low concentrations. In conclusion, it is a good adsorption property of heavy metal (zinc) in water by modified corncob.