This study aimed to investigate the effects of different oligosaccharides on the quality and volatile aroma compounds of fermented green tea. Sucrose, isomalto-oligosaccharides, galacto-oligosaccharides, and fructo-oligosaccharides were added to Mao Jian green tea extract and subjected to fermentation with Lactiplantibacillus plantarum at 37 ℃. Changes in physicochemical properties, monomeric phenolic compounds, antioxidant activity, organic acid composition, and volatile compounds were analyzed before and after 48 h of fermentation. The results showed that, compared with sucrose-supplemented fermented green tea, oligosaccharide supplementation significantly increased total phenolic and flavonoid contents, monomeric phenol content changed significantly (P<0.05). Among them, galacto-oligosaccharide supplementation yielded the highest total phenolic content (2552.21 mg GAE/L), while isomalto-oligosaccharide supplementation yielded the highest total flavonoid content (365.83 mg RE/L). Oligosaccharide supplementation also markedly enhanced antioxidant activity (P<0.05). Galacto-oligosaccharide supplementation produced the strongest DPPH radical scavenging activity (79.20%) and ferric-reducing antioxidant power (23.95 mmol Trolox/L); however, fructo-oligosaccharide supplementation produced the highest ABTS⁺ radical scavenging activity (89.40%). In addition, significant differences (P<0.05) in organic acid were observed between oligosaccharide-supplemented samples and sucrose-supplemented samples. Oligosaccharide-supplemented samples had higher total volatile aroma compound levels than sucrose-supplemented samples, with increased alcohol, alkene, and ketone levels, and the formation of new volatile aroma compounds, such as isoamyl alcohol, lauric acid, and ethyl acetate, thereby conferring distinctive aroma characteristics. Among the oligosaccharides, isomalto-oligosaccharide supplementation yielded the highest volatile aroma compound content (43987.09 μg/L). Overall, these findings indicate that oligosaccharide supplementation not only significantly enhances the nutritional composition and antioxidant activity of fermented green tea but also enriches its aroma profile, providing a theoretical basis for the development of functional fermented tea products.