Abstract: Abstract: Oxidative deterioration of oil and protein is a common problem in the food industry, which led to trending studies of safe antioxidants with strong antioxidant activity. Ctenopharyngodon Idellus is a commercial fish, which is rich in proteins and polyunsaturated fatty acids, and is widely distributed in fresh-water throughout China,. In recent years, the Ctenopharyngodon Idellus was prepared as condiment or nourishment, however, further studies are limited. In this study, Ctenopharyngodon Idellus was hydrolyzed by three proteases (papain, PTN6.0, and Alcalase2.4 L), and the hydrolysate was isolated at two fractions of molecular weight above and below 5 kD by ultrafiltration. The fraction below 5 kD (Ctenopharyngodon Idellus peptide) was heated with or without xylose at 100 ℃ for different times (30 min to 240 min). Oxygen radical absorbance capacity (ORAC), reducing power, UV absorption, and volatile components of Maillard reaction products (MRPs) and thermal degradation products (TDPs) with different reaction times were evaluated, respectively. This study focuses on the effects of Maillard reaction on the antioxidant activity and the volatile components from Ctenopharyngodon Idellus peptide and its derivatives. The correlation between reaction products, volatile components, and their antioxidant activity were also analyzed. Results revealed that the browning intensity and UV absorption of the intermediate products of MRPs were much higher than those of TDPs. Antioxidant activity of MRPs increased with increasing heat time, while TDPs had no obvious change. In addition, MRPs showed better antioxidant activity. Reducing power and oxygen radical absorbance capacity of MRPs for 240 min was 17.77 and 3.32 times than those untreated. 51 kinds of volatile compounds were separated and identified from MRPs; among them, pyrazines, furans, pyrroles, aldehydes, ketones, and alcohols had relatively high concentration. Whereas, aldehydes were the largest content of volatile compounds in TDPs (above 80 percent), little furan, ketones, and alcohols were also observed. In summary, the antioxidant activity of Ctenopharyngodon Idellus peptide could be increased obviously by Maillard reaction. There was significant correlation (P > 0.95) between Maillard reaction products and antioxidant activity. Thus, MRPs of peptide from enzymatic hydrolysis can be used as a new type of natural antioxidant.