The invention provides a production method of a blackberry and purple sweet potato compound juice and a product of the production method, belonging to the technical field of deep processing of agricultural products. The production method of the blackberry and purple sweet potato compound juice comprises the following steps: carrying out washing treatment on purple sweet potatoes and blanching, adding water with the mass ratio of purple sweet potatoes to water of 1:2, and pulping at a high speed; carrying out enzymolysis on an obtained pulp with medium temperature-alpha amylase to obtain a purple sweet potato pulp, carrying out washing treatment on blackberries, adding water with the mass ratio of blackberries to water of 1:1, and pulping at a high speed to obtain a blackberry pulp; mixing the purple sweet potato pulp and the blackberry pulp with the mass ratio of 2:1; carrying out composite enzymolysis on the mixed pulp with cellulase and glucoamylase, carrying out enzyme deactivation at high temperature and centrifugally filtering the mixed pulp. According to the invention, the compound juice can reach an ideal acidity by using high-content tartaric acid in the blackberries and thus the convenience is brought for enzymolysis and drinking; and as starch and cellulose in the sweet potatoes are converted into to sugar by enzymes, the compound juice can reach an ideal sweetness, and the juice yield, the content of solids and the content of anthocyanin are all increased. The blackberry and purple sweet potato compound juice is natural and safe for an acidulant and a sweetener do not need to be added in the compound juice, and is broad in marketing development prospect.