Abstract: The present disclosure discloses a method for liquid fermentation of black tea juice by using aged green tea and belongs to the technical field of tea leaf processing. The method comprises the following process steps: mixing aged green tea with hot water for a water bath-assisted extraction; adding a tannase into a crude catechin extract for a water bath-assisted enzymolysis; freeze-withering fresh tea leaves; homogenizing the freeze-withered leaves; pouring a homogenate into a primarily enzymolyzed crude catechin extract, adding a ?-glucosidase for secondary enzymolysis and performing fermentation; and treating a fermentation broth by microwave, and performing filtration and cooling to a room temperature.