Abstract: Objective: To separate the best active fraction of Maillard reaction products( MRPs) of Fructus corni by ultrafiltration and compare the properties and antioxidant activities of different molecular weight cutoffs of Fructus corni MRPs.Methods: Fructus corni was adopted as substrate for Maillard reaction and MRPs were obtained after reactions at high temperature.The MRPs were ultrafiltered by hollow fiber membrane of 0.45 μm,0.22 μm,100 ku,50 ku,10 ku,4 ku,and then lyophilized to get different molecular weight cutoffs of Fructus corni MRPs.Physical and chemical properties of different molecular weight cutoffs were determined,and the radical scavenging ability on DPPH radical and the reducing ability of potassium ferricyanide were also observed. Results: The UV absorption curves of different molecular weight cutoffs were similar and the maximum absorption was all at 284 nm. Among different molecular weight cutoffs of Fructus corni MRPs,cutoffs of 0.45~0.22 μm had the highest browning degree and strongest scavenging ability on DPPH radical and reducing ability of potassium ferricyanide. Conclusion: It suggests that the best antioxidant active fraction of Fructus corni MRPs are super- macromolecules with size of0.45~0.22 μm.