Objective To investigate the effects of probiotic fermentation conditions and drying methods on the quality of fermented sea buckthorn leaf products.Methods Lactiplantibacillus plantarum is used for fermentation. The fermentation process of sea buckthorn leaves is optimized through single-factor experiments combined with response surface methodology. Fermented sea buckthorn leaf extract is prepared under the optimal fermentation conditions and subsequently processed into freeze-dried powder by direct freeze-drying and spray freeze-drying, with or without low-voltage electrostatic field assistance. The effects of different treatments on viable cell counts, flavonoid and polyphenol retention rates, water activity, and in vitro digestion characteristics are evaluated.Results The optimal fermentation conditions are determined as follows: 8% sea buckthorn leaf powder, 2% L. plantarum inoculum, initial pH 5, fermentation temperature of 36 ℃, and fermentation time of 72 h. Under these conditions, flavonoid and polyphenol content is significantly increased. Drying methods have significant effects on product quality. The spray freeze-dried samples exhibit the lowest water activity and higher retention rates of flavonoids and polyphenols. However, their viable cell survival rate is significantly lower than that of the direct freeze-dried samples (P0.05). During simulated in vitro digestion, the product shows continuously decreasing viable cell counts, dynamic changes in flavonoid content, and an overall declining trend of polyphenol content.Conclusion Spray freeze-drying is more suitable for producing products rich in bioactive compounds, whereas direct freeze-drying is more favorable for maintaining probiotic viability.