To identify the changing pattern of nutrition, flavor components, and antioxidant activity, some critical indexes were estimated in tea beverage fermented from plant lactobacillus in tartary buckwheat sprout. These indexes included the content of rutin, quercetin, kaempferol-3-O-rutinoside, total flavonoids, and amino acids, as well as volatile compounds identification, including the radical scavenging rate of DPPH and ABTS in buckwheat sprout beverage. The results showed that the content of rutin remained unchanged, but quercetin and kaempferol-3-O-rutinoside decreased slightly, and the total flavonoids decreased slightly from (120.6±1.9) μg/mL to (114.6±1.7) μg/mL after fermentation. Tea beverage of tartary buckwheat sprout contains six kinds of EAA and eleven kinds of NEAA. After fermentation, the ratio of EAA/TAA and EAA/NEAA were 38.32% and 62.13%, respectively, which was significantly increased as compared to pre-fermentation. 54 kinds of volatile substances were identified, including 46 in pre-fermented beverage and 43 in post-fermented beverage, and could be classified into 8 categories. Further analysis indicated that the content of aromatic flavor substances with lower threshold was significantly increased after fermentation. The free radical scavenging rate of DPPH and ABTS were both enhanced after fermentation, implied the improved antioxidant activity of tea beverage of tartary buckwheat sprout through lactobacillus fermentation.