A new method for the analysis of coumarin constituents in the roots of Peucedanum japonicum by high performance liquid chromatography was established. Among two coumarin constituents identified, peucedanol was confirmed to be applicable to a standard compound. A reversed phase system with a ${mu}Bondapak$ C_{18}$, column using $H_2O-MeOH=5;:;4$ as a moble phase was developed. Peucedanol and a minor constituent, umbelliferone were detected at 333nm and the analysis was successfully carried out within 20 min.