Abstract: ¹³C breath test has been widely used in research of nutrition,pharmacology and gastroenterology for its properties such as safety,noninvasion and so on.This review describes the principle,methodology of ¹³C breath test and its application in detection to Helicobacter pylori infect ion in stomach and small bowl bacterial overgrowth,measurement of gastric empt ying,pancreatic exocrine function and liver function with various substrates.