A new method for quantitative determination of byakangelicin in Angelicae dahuricae Radix by high performance liquid chromatography was established. A reversed-phase system with a ${mu}Bondapak$ $C_{18}$ column using THF : dioxane : MeOH : HAc : 5% $H_3PO_4$ : $H_2O$=72.5 : 62.5 : 25 : 10 : 1 : 329 as a mobile phase was developed. Byakangelicin together with ter-O-byakangelicin and oxypeucedanin methanolate, and isooxypeucedanin as an internal reference were detected at 350 nm and the analysis was successfully carried out within 30 min.