Abstract: In manufacture of black tea, one of the most important steps is fermentation which significantly influences the sensory quality of tea. Under the condition of certain temperature, humidity and oxygen concentration, tea polyphenols presented in macerated leaves get oxidized to form TFs, TRs, TBs and other polymers, and aromatic substances, carbohydrate and protein change dramatically during the fermentation stage of black tea processing. The main functions of important enzymes in black tea fermentation, including polyphenol oxidase, peroxidase, β-glycosidase and lipoxygenase, and change rules of the main biochemical compositions including polyphenols, proteins, sugars, amino acids and aromatic substances were summarized in this paper. Besides, the author focused on the auxiliary techniques and new fermentation techniques such as suspension fermentation, oxygen supply fermentation and exogenous additive fermentation. The control of fermentation environment parameters were reviewed as well, such as temperature, humidity, light and oxygen concentration. Based on these theoretical researches, the main mechanism of fermentation and the development of new fermentation equipment were prospected for further study of fermentation of black tea.