Zanthoxyli Fructus has been used in traditional medicine for the treatment of analgesic, gastric disorder, rheumatism etc. In order to evaluate the quality of Zanthoxyli Fructus, the method of isolation and quantitative determination of xanthoxylin as a standard compound has been developed. The HPLC method, using the mobile phase of acetonitrile-water (4:6), showed that the amount of xanthoxylin wεre in the rangε of 0.01 to 2.67%.