In this study, Maojian, crushed black tea and zymic Pu'er tea were chosen as representative of non-fermented, fully-fermented and post-fermented tea, respectively. The composition profiles of ethanol/water extracts were compared, and the antioxidant activities in vitro were detected by oxygen radical absorbance capacity (ORAC) and DPPH assay. In order to confirm the contribution of each key functional contributors, recombination model of antioxidant compounds in tea have been built and studied. The results showed that ethanol extracts contained higher contents of tea polyphenol, caffeine and prolamin, and higher antioxidant activities detected by ORAC and DPPH assay, while higher amounts of tea polysaccharide, gallic acid and theanine were found in water extract. Correlation analysis showed that antioxidant capacities of tea extracts were mostly influenced by ester catechins, such as ECG and EGCG. The results of recombination test showed that catechins and gallic acid were the major compounds responsible for antioxidant activity of Maojian extract, whereas other bioactive compounds might also exist in fermented tea, i.e., crushed Black tea and zymic Pu'er tea.