The invention discloses a method for preparing astringent persimmon powder with high micromolecule tannin content. The method comprises the following steps of: washing, smashing and juicing almost ripe persimmons, and performing enzymolysis, color protection, filtration, enzyme deactivation, sterilization and vacuum degassing, thus obtaining original persimmon juice; performing microfiltration onthe original persimmon juice by use of a microfiltration film with the porosity of 0.22 mu m, performing primary ultrafiltration by use of an ultrafiltration film capable of retaining the molecular weight of 20,000, performing secondary ultrafiltration by use of an ultrafiltration film capable of retaining the molecular weight of 1,000, and collecting a filtrate obtained by the secondary ultrafiltration; and directly or further concentrating the filtrate, freezing and drying, thus obtaining the astringent persimmon powder with high micromolecule tannin content. Compared with the prior art, the method has the advantages that materials in all working procedures are at the temperature less than 60 DEG C, and most active substances in the persimmons are retained; and the astringent persimmon powder is high in quality and high in micromolecule tannin content, can be used as an anti-radiation, anti-oxidization and adsorption material, and is wide in application prospect.