Functional dyspepsia (FD) is a clinical syndrome with persistent or recurrent upper abdominal pain or discomfort, and organic diseases have been excluded after examination. According to clinical manifestations, FD can be further divided into different subtypes: postprandial discomfort syndrome (PDS) (early satiety or postprandial fullness) and epigastric pain syndrome (EPS) (pain or burning sensation in the upper abdomen). FD, belching (including aerophagia and nonspecific belching), functional nausea and vomiting (including chronic idiopathic nausea, functional vomiting and cyclical vomiting), and rumination syndrome are all functional gastroduodenal diseases. Epidemiological surveys show that patients with dyspepsia symptoms account for about 30% of the total number of outpatient clinics in internal medicine and 70% of the outpatient clinics in gastroenterology. Among them, functional dyspepsia accounts for 30% to 40% of the outpatient clinics in gastroenterology.