Abstract: Activated components of parasiticidal Dactylogyrus intermedius extracted from Radix angelicae pubescentis were isolated and purificated by column chromatography and biologica l tracking in this study. The activity in vitro of activated components at different concentrations were determined. Then their chemical structures were identified by TLC, UV, HPLC and GC-MS. Observations implied that the killing effect of the components on D. intermedius at different concentrations were fraction Fand K1-2-3. Fraction F could reach to 100% parasiticidal rate when the concentration was 1.6 mg/L. As for K1-2-3, concentrations of 5 mg/L could reach to the parasiticidal rate of 74.9%. According to physico- chemical property examination and spectroanalysis, fraction F and K1-2-3 were identified as the osthole and scopoletine.