Abstract: With epigallocatechin gallate (EGCG) and four proteins (soy protein isolate, casein, egg white albumin, and β-lactoglobulin) as materials, one protein-EGCG non-covalent complex and three covalent complexes were prepared through mixing, coupling reaction, hydroxyl radical reaction, and enzymatic reaction, respectively in this study. Indicators (such as EGCG binding rate, antioxidant in vitro, and inhibition rate of aging enzymes) were detected to examine effects of protein type and combination mode on EGCG binding status and activities in vitro of protein-EGCG complexes, and their correlation between the activity in vitro and structural stability during the digestive process were determined. Results showed that when protein-EGCG complexes forming, abilities of EGCG to scavenge the free radical (DPPH· and OH·) and inhibit aging (tyrosinase and elastase inhibition) were enhanced differently with the varied protein type and the binding mode. Although having the largest EGCG binding amount (0.175~0.225 mg/mg pro), casein-EGCG complexes were also discovered lower activities in vitro than complexes containing soy protein isolate and EGCG under the same combination mode. Activity of the protein-EGCG non-covalent complexes could be improved by the hydroxyl radical covalent reaction owing to their enhanced DPPH· scavenging rate and tyrosinase inhibition rate by more than 86.73% and 49.12% respectively, while effects of enzymatic reactions and alkali oxidation reaction were opposite. The activities in vitro of protein-EGCG complexes were found irrelevant to their EGCG binding amount, but may be related to their structural stability. With a poor digestive stability (EGCG binding amounts ranging from 0.06 to 0.15 mg/mg Pro), soy protein isolate-EGCG covalent complex prepared by hydroxyl radical reaction, was discovered to show superior extracellular antioxidant activity, confirming the inverse correlation between the extracellular activity of protein-EGCG complexes and their structural stability to some extent.