The invention discloses a method for reducing loss of anthocyan of blueberry fruit juice in a processing course. The method comprises the following steps of (1) cleaning blueberries, and performing mashing to obtain blueberry slurry; (2) regulating the pH value of the blueberry slurry, adding zinc lactate, malic acid, glutathione, tea polyphenols and a grape seed extract to the blueberry slurry, and then adding complex enzymes; (3) after performing enzymolysis on the blueberry slurry, performing filtering, adding cane sugar, lactose, sodium citrate, trehalose, beta-cyclodextrin, arabic gum, xanthan gum and sodium carboxymethyl cellulose and performing allocation; (4) homogenizing the allocated fruit juice, and then performing vacuum degassing; and (5) sterilizing the degasses blueberry fruit juice and performing filling. In accordance with special functional components of the anthocyan in the blueberries, in the processing course of the blueberry fruit juice, in two respects that processing factors are controlled, and the self molecular structure stability is improved, the degradation loss of the anthocyan in the blueberries is reduced, the efficacy is reserved, the color deterioration is alleviated, the product quality is improved, and a blueberry fruit juice product high in anthocyan content is developed.