OBJEC TIVE To establish the qu ality standard of Hylocereus undatus ，and to provide reference for its quality control. METHODS The sample of H. undatus medicinal materials was collected for character observation ，powder microscopic identification and thin-layer chromatography （TLC）identification. Moisture content ，total ash ，acid-insoluble ash ，water-soluble extracts and alcohol-soluble extracts were determined according to the corresponding methods in the general provisions of the 2020 edition of Chinese Pharmacopoeia （part Ⅳ）. The contents of kaempferol and isorhamnetin in H. undatus were determined by high performance liquid chromatography. RESULTS The medicinal materials of H. undatus were in brown or yellowish brown irregular long bundles ；the calyx tubes were twisted in bundles ；the scales on the outside of the flower were shrunken ，and many stamens were inserted on the inside. The powder was brown-green or brown-yellow ，and pollen grains ，ducts and non-glandular hairs were found.In the TLC diagram of test sample ，fluorescent spots of the same color were displayed on the corresponding position of the chromatogram of substance control （kaempferol， isorhamnetin） and reference material. The moisture content ， total ash ， acid-insoluble ash ，water-soluble extract and alcohol-soluble extract of the 15 batches of samples ranged from 10.70％ to 12.23％， 7.48％ to 11.29％，0.25％ to 0.70％，30.34％ to 49.91％，and 25.27％ to 36.92％，respectively. The average values were 11.44％，9.51％，0.46％，40.13％，32.33％，respectively. The contents of kaempferol and isorhamnetin were 1.787-3.785 and 0.597-2.211 mg/g，respectively. CONCLUSIONS This study add microscopic identification ，TLC identification and inspection items such as moisture content ，ash and extract on the basis of the existing quality standards of H. undatus . It is preliminarily proposed that the moisture content in H. undatus shall not exceed 13.0％ and total ash content shall not exceed 12.0％，and the water-soluble extract and alcohol-soluble extract shall not be less than 30.0％ and 25.0％ respectively；the contents of kaempferol and isorhamnetin shall not be less than 1.780 and 0.590 mg/g，respectively. The established quality standard can be used for quality control of H. undatus .