The effects of gallic chatechin gallate (EGCG) on the digestion properties and protein oxidation of sea bass fillets by microwave heaing was studied. By simulating the gastrointestinal digestion process， the digestibility， particle size， carbonyl， free sulfhydryl， free amino acid contens changes and the morphology of the digestion products were determined. The results showed that digestion of sea bass fillets was basically completed at 40 min， and the protein digestibility was 75.23%. The sea bass slices by EGCG-treating were digested for a longer time， but there was no significant effect on the digestibility. After 120 min of intestinal digestion， the protein digestibility reached 72.13%~76.16%. The carbonyl content in gastric digestion was significantly higher than that in intestinal digestion. After 40 min of digestion in the intestine， the carbonyl content was decreased by 20.76%-30.58%. EGCG delayed the reduction of free sulfhydryl content， and reduced the oxidation level of protein. The particle size in the digestion product system of the EGCG treatment group decreased in concentration-dependent type and reduced the micromorphological aggregation， while reducing the content of free amino acids.