Abstract: Objective:Free radical models and a microplate reader were used to explore the scavenging activity of Caffeic acid derivatives against hydroxyl and DPPH free radicals. Methods:The CuSO₄ -Phen-V_C -H₂O₂ -DNA chemiluminescences system was employed to determine the inhibitory effect of ChA, FeA and RoA on hydroxyl radical-induced DNA damage. Meanwhile, the protective effect and possible mechanisms of the three phenolics compounds with effective concentration against free radical-induced DNA damage were also explored. Results:The DPPH· scavenging ratio was 28.93% , 58.39% , 83.93% and 84.09% , respectively when the CADs concentration was at the 25, 50, 100, 200μg/mL within 30min reaction. The clearance of ·OH were 33.43% , 55.27%, 71.23%, 77.49%. The inhibition ratio of the chemiluminescence of DNA damage product were 12.49%～81.09% . With different CADs concentrations of 25²00μg/mL, and the time of DNA damage was delayed. Conclusion:CADs could scavenge DPPH· and ·OH obviously and restrain the DNA injury caused by the free radical, or delay the DNA damage time. The scavenging free radical and protective effect of CADs on DNA damage was related to its concentration. The effect was the strongest on DPPH scavenging, the luminescence inhibition rate of DNA damage product and the ability to protect the DNA damage was three CADs joint group, reflect a certain synergy.