Objective: To investigate the value of duodenal bulb ultrasonic anatomy locating method quickly confirm nasointestinal tube placed below pylorus in critically ill patients. Methods: A total of 56 critically ill patients with nasointestinal tube posting surgery by blindly inserting method were collected from March 1 st, 2016 to August 1 st, 2016 in the Department of Critical Care Medicine of Zhejiang Provincial People's Hospital.In these patients, the duodenal bulbs were rapidly detected and located by ultrasonic anatomy locating method and at the same time observed whether nasointestinal tube echogram were in them or not. If nasointestinal tube echogram was observed in duodenal bulbs that meant nasointestinal tube placed below pylorus successfully. If disturbed by ultrasound artifacts or other reasons, injected gas into the nasointestinal tube could help to confirm when hyperechoic strip emerged. Gastrointestinal decompression or gastrointestinal motion promoting drug could help to reduce the interference of abdominal cavity or bowel gas if necessary. The results were compared with the abdominal X examination to vertify the accuracy of this method, and at the same time recorded its total time-consuming and its related complications. Results: The duodenal bulbs were rapidly located by ultrasonic anatomy locating method in 53 cases(94.6%) time-consuming(42±23)s. Nasointestinal tubes observed in duodenal bulb were confirmed to be placed below pylorus successfully in 52 cases(92.9%)time-consuming(140±94)s.There were no obvious complications in all patients. Conclusion: Duodenal bulb ultrasonic anatomy locating method is a safe, simple and convenient method with high accuracy that can quickly confirm whether nasointestinal tube placed below pylorus in critically ill patients or not.