【Objective】The purpose of this study was to investigate the changes in quality ingredients and primary enzyme activities of Sichuan dark tea during post-fermentation.【Method】The quality ingredients and primary enzyme activities of Sichuan dark tea were monitored during the entire post-fermentation using national standard measuring methods and some common measuring methods.【Result and conclusion】The results showed that except for caffeine, the contents of polyphenols, catechins, theaflavins, thearubigins, theabrowns, cellulase, pectin, protein, amino acid, soluble pectin, and soluble sugar declined by 69.2%, 43.7%, 79.3%, 81.7%, 52.4%, 9.6%, 60.0%, 62.3%, 66.2%, 32.2%, and 37.2%, respectively, in the process of post-fermentation. The activities of polyphenol oxidase, peroxidase, cellulase and pectinase increased to the maximum on the 19th, 12th, 17th and 17th day of post-fermentation process, respectively, and they increased by 246%, 371%, 371% and 223%, respectively, compared with the beginning of post-fermentation. The variation of the quality ingredients and primary enzymes of Sichuan dark tea during post-fermentation is complex, which contributes to the formation of quality characteristics of Sichuan dark tea.