In order to remove the residual harmful lead ion(Pb2+) in water, modified multi-walled carbon nanotubes (O-MWNTs), as a adsorbent, was used to enrich and remove Pb2+ in water samples. O-MWNTs was obtained by mixed acid oxidation. It was analyzed and confirmed that O-MWNTs had been obtained successfully by FITR and TEM. The adsorption property of O-MWNTs to Pb2+ in water was investigated. The adsorption efficiency of adsorbent dosage, adsorption time, adsorption pH and adsorption temperature was investigated, and conclusions are as follows: when pH is 5, the temperature is 20℃, adsorption time is 40 min, and adsorbent dosage is 40 mg/L, the adsorption efficiency was the highest. Adsorption rate of can reach 81.7% under optimal conditions.