Tartary buckwheat seedlings after germination contain abundant beneficial ingredients, especially flavonoids. In this study, tartary buckwheat seedlings and buckwheat tea juice were fermented by Lactobacillus plantarum. The fermentation conditions and formula were optimized by single factor and response surface optimization experiments, and the flavonoids content, light transmittance and pH of pro-ducts were determined. The results showed that the optimal ratio of tartary buckwheat seedlings to tartary buckwheat tea juice was 1∶6, and the dilution rate of better supernatant was 1∶10. And the total flavonoids content of products could reach (0.193±0.006)mg/mL. The optimal fermentation conditions were 0.6% microbial inoculum, fermentation time 24h, and 6% fructose-glucose syrup. Under this condition, the average sensory score of product was 91.50±0.29 and the optimum pH value was 3.87±0.05. The best stabilizer formula of this beverage was 0.06% xanthan gum, 0.08% CMC-Na, and 0.05% sodium alginate. Under this condition, the average sensory score was 93.60±0.32 and the transmittance was 91.37%±0.45%. After fermentation, this beverage is rich in flavonoid probiotics, and other beneficial ingredients, which had a mellow taste, clear and unique flavor.