Abstract: Objective: To improve the taste of sea buckthorn juice and remove the bitter substance isorhamnetin glycoside. Methods: Fermentation of sea buckthorn juice with Lactiplantibacillus plantarum to study the growth curves of probiotics, the changes of various indexes such as total phenolic content and antioxidant activity during the fermentation process, as well as the changes of isorhamnetin glycosides and isorhamnetin content. Results: The sea buckthorn juice fermented by Lactiplantibacillus plantarum 67-25-2 fermentation had its bitter flavour improved and the sensory analysis score reached 85, and the total free phenol content and antioxidant activity of the juice were increased, reaching maximum at 62 h, in which the total phenol content was increased to 598.9 mg GAE/L, and the scavenging rate of the ABTS⁺ free radicals and the DPPH free radicals were reached 67.5% and 61.8%, respectively. Pearson correlation analysis revealed that total phenol content and isorhamnetin content were significantly positively correlated with DPPH radical scavenging and ABTS⁺ radical scavenging (P<0.01). Conclusion: The main bitter substance in sea buckthorn, isorhamnetin-3-O-neohesperidin, was significantly (P<0.05) reduced by the fermentation of Lactiplantibacillus plantarum 67-25-2, which also significantly (P<0.05) increased the total phenol content and antioxidant activity. This research can serve as a theoretical foundation for the development of functional fermented sea buckthorn foods that contain highly active transformation products and methods for enhancing the taste of sea buckthorn fruit.