•A new evaluation assay combined in vitro digestion with CAA was built.•Digesta had higher FPA but lower TPC and TAC than extracts.•Digesta had higher CAA but lower ABTS, FRAP, DPPH, ORAC than extracts.•TPC had higher correlation than TAC with CAA in digesta.•Digestion improved the correlation between CAA values and total phenolic contents. The traditional method of chemical extraction (i.e., extracts), combined with chemical antioxidant activity assays cannot assess the real antioxidant activity. In vitro digestion (i.e., digesta) with a cellular antioxidant activity (CAA) assay was developed for the determination of antioxidant activity in Chinese bayberry fruits. In this study, pretreatment methods were studied and the results showed that digesta had more free phenolic acids (FPA) but less total phenolic content (TPC) and total anthocyanin content (TAC) than extracts. Antioxidant activity assays, including ABTS, FRAP, DPPH, ORAC and CAA, were compared. Digesta had lower ABTS, FRAP and DPPH values but higher CAA values than extracts. FPA were better correlated with the chemical antioxidant assays in digesta. The correlations were high between TPC and CAA values in digesta (R2=0.96) but not extracts (R2=0.58). Higher correlations were also obtained between CAA and chemical assays in digesta.