Objective: The contents of tea polyphenol monomer, caffeine (CAF), total polyphenols acid (TPC) and total flavonoids (TFC) in 26 kinds of commercial Sichuan dark tea (S1～S26) were analyzed, and the in vitro antioxidant activities were investigated, to provide a theoretical basis for the quality evaluation of Sichuan dark tea. Methods: Gradient elution was used to analyze the content of tea polyphenol monomer and caffeine. The contents of TPC and TFC were determined by the folin phenol method and chemical analysis method, respectively. The antioxidant activity was evaluated by DPPH and ABTS radical scavenging capacity. Results: The content of gallic acid (GA), gallocatechin (GC), epigallocatechin (EGC), catechin (C), epicatechin (EC), epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), epicatechin gallate, catechin gallate (CG), caffeine (CAF), total polyphenols acid (TPC), total flavonoids (TFC) were 0.26~19.64, 0.72~4.73, 0.00~20.28, 0.00~0.95, 0.00~6.06, 0.32~9.44, 0.62~63.12, 0.29~17.08, 0.21~1.81, 9.53~44.43, 20.96~279.05 and 7.92~17.49 mg/g, respectively. The free radical scavenging activity of ABTS was 33.49～232.87 mg/g based on a water-soluble VE equivalent. Moreover, that of DPPH was 45.26～237.59 mg/g correlation analysis results showed that DPPH scavenging abilities positively correlated with the ten monomers, CAF, TPC, and TFC (P＜0.05 or P＜0.01). However, ABTS radical scavenging abilities positively correlated with the contents of GC, GA, and CAF (P＜0.01), also positively correlated with TPC and TFC (P＜0.05). Conclusion: PCA results showed that the cumulative contribution rate of EGCG, C and TPC was 87.566%. According to the comprehensive analysis, S16, S23 and S19 had higher scores, implying relatively better quality. The variations of the results should be attributed to the raw materials, production technology, and storage conditions of dark tea.