The dominant fungi in Fuzhuan tea produced in Hunan were isolated and identified by morphological analysis and comparative analysis of internal transcribed spacer (ITS) sequences. Then, single-strain fermentation of low-grade Yunnan large-leafed green tea was carried out using the isolated fungi, and changes in the contents of the main components of green tea were analyzed before and after fermentation. The results showed that four dominant strains named as J1-J4 were isolated from Fuzhuan tea. J1 was identified as Aspergillus chevalieri, and J2, J3 and J4 as Aspergillus cristatus. The contents of tea polyphenols and total flavonoids in green tea significantly fell after fermentation, whereas the content of theabrownin increased significantly. The total alkaloid content significantly increased after fermentation with A. chevalieri, but significantly decreased after fermentation with A. cristatus. The contents of catechin components varied significantly after fermentation; ester catechin content decreased significantly, while the contents of three non-ester catechins (epicatechin, gallocatechin, and epigallocatechin) increased significantly. Theaflavin content was significantly decreased by strains J1, J2 and J3 but significantly increased by strain J4. The contents of amino acids also changed significantly. The results of this study can provide a theoretical basis for the development of high-value products from low-grade Yunnan large-leafed green tea.