Objective To investigate the effect of preoperative preplacement of nasobiliary drainage in radiofrequency ablation of small hepatocellular carcinoma at hepatic portal. Methods 7 patients with small hepatocellular carcinoma who were admitted to our hospital from June 2014 to June 2017 were selected. All patients were the cases who were prone to injure the bile duct at hepatic portal upon the radiofrequency electrode needle entering liver cancer in the small hepatocellular carcinoma at hepatic portal. The nasal bile duct was pre-placed preoperatively, and infusion of water into nasobiliary bile duct was conducted to expand the bile duct for intraoperative identification and avoiding false puncture. In some cases, after intraoperative bile duct injury, postoperative nasobiliary drainage was given to avoid obstructive jaundice or the occurrence of bile tumor at hepatic portal. Results The treatment effective rate in the patients was 100％ (7/7). Blood biochemistry, routine blood test, liver function were re-examined after surgery. Liver CT or MRI was reexamined 30 to 60 d after surgery. After the preplacement of nasal biliary, there was one case of pancreatitis, with the incidence rate of complications of 14. 3％. The long-term treatment effect was favorable, without tumor recur-rence. Conclusion For small hepatocellular carcinoma at hepatic portal, preoperative preplacment of nasobiliary drainage is used, and the direction of the bile duct during radiofrequency ablation can be clearly observed, so as to effectively avoid the bile duct injury.