Abstract: The synergistic effect between round scad protein hydrolysate( RSH- III) and other antioxidants( GSH and vitamin C) was investigated through DPPH·and O₂^-·scavenging activity methods.Among all combinations,groups of RSH- III and GSH,RSH- III and vitamin C exhibited no synergist effect when scavenging DPPH· at low concentration range from 0.2 g·L^-1to 0.4 g·L^-1,but significant negative synergy was observed on the higher concentration of 0.8 g·L^-1. In the scavenging O₂^-· research,there was only negative synergy effect exhibited at high concentration of GSH( 2.5 × 10- 3g·L^-1~4.2 × 10- 3g·L^-1).The O₂^-·radical scavenging effect was independent on the concentration for the combination of RSH- III and vitamin C,significant negative synergy was observed at all of the concentration.The research laid a good foundation for application of round scad hydrolysate,which could be used to guide the efficient application of antioxidative peptide.