Abstract: In order to make full use of the chestnut shell resources,four procyanidins sample with different polymerization degree F1(70% ethanol extract),F2(AB-8 macroporous resin purification),F3(ethyle acetate extract)and F4(water-soluble fraction)were extracted from fresh chestnut shell were measured for mean degree of polymerization. In vitro antioxidative and antibacterial activity of procyanidins in chestnut shell was analyzed. The compositions of the part with highest activity were analyzed by high performance liquid chromatography(HPLC)and high resolution mass spectrometry(HRMS). The results showed that the mean degrees of polymerization of F1,F2,F3 and F4 were 9.42±0.41,4.14±1.06,3.32±0.34,5.07±0.75,F3 with the smallest degree of polymerization had the highest antioxidant activity. It had the best scavenging rate against ABTS radical,hydroxyl radical and superoxide anion radical with the IC₅₀ values of 11.24,1.18 and 93.98 μg/mL,respectively. The preliminary screening of the inhibition zone experiment showed that F1 had inhibitory effect on Staphylococcus aureus,the inhibition on Escherichia coli and Salmonella were not obvious. Staphylococcus aureus was the indicator,antimicrobial activities of four procyanidins with different polymerization degree were measured. The results of measurement showed that F3 with the smallest degree of polymerization had significant bacteriostatic effect on Staphylococcus aureus,and the minimal inhibitory concentration(MIC)was 0.31 mg/mL. The results of HPLC and HRMS showed that gallic acid,catechin/epicatechin and B-type procyanidin were present in F3.In conclusion,chestnut shell proanthocyanidins have good antioxidant and bacteriostatic activity,and the antioxidant and bacteriostatic effects of low-polymerization proanthocyanidins were more significant. They could be used as raw materials for natural antioxidants and bacteriostatic.