Objective:To explore the efficient extraction method of organic selenium from selenium-rich tea and its occurrence form.Methods:The continuous dialysis method and the subtraction method were used to optimize the extraction method of organic selenium. At the same time, the four proteins (water-soluble, salt-soluble, alcohol-soluble, alkali-soluble proteins) were sequentially extracted according to the classification and properties of Osborne soluble proteins. In vitro simulation technology was used to simulate the digestion process of selenium in selenium-rich tea in the gastrointestinal fluid, and the bioavailability of human intake of selenium and the occurrence form of organic selenium were further analyzed by atomic fluorescence spectrometer-liquid chromatography. Results:The total selenium content of selenium-rich tea was (303.12 ± 1.19) μg/kg. The contents of organic selenium measured by the continuous dialysis method and the subtraction method were (154.76 ± 9.47) and (265.02 ± 6.55) μg/kg, respectively, the difference was statistically significant ( t=- 2.56, P < 0.05). The contents of four proteins in descending order were alkali-soluble protein (29.79 g/100 g), water-soluble protein (2.52 g/100 g), salt-soluble protein (2.15 g/100 g), and alcohol-soluble protein (1.04 g/100 g), respectively. After digestion simulation of gastrointestinal fluid, the selenium content of tea samples was (203.01 ± 3.16) μg/kg, and the bioavailability of selenium was 66.97%. The content of selenomethionine (SeMet) in alcohol-soluble protein was (13.87 ± 3.21) μg/kg, and the content of selenocysteine (SeCys) was (0.82 ± 0.38) μg/kg; the content of SeMet in alkali-soluble protein was (2.59 ± 2.16) μg/kg. Conclusions:In the extraction method of organic selenium from selenium-rich tea, subtraction method is better than continuous dialysis method. SeMet in selenium-rich tea can be detected in alcohol-soluble and alkali-soluble proteins, and SeCys can be detected in alcohol-soluble protein.