Using Phenomenex C18 column and low pressure gradient elution with mobile phase of methanol (A) -0. 1% phosphoric acid water solution (B), isofraxidin content in 70% methanol extracts from root, stem and leaf of Chloranthus japonicus Sieb. was determined by HPLC. The results show that isofraxidin mainly exists in the chloroform. partitioned extracts from 70% methanol extracts. Average content of isofraxidin in root, stem and leaf of C. japonicus is 0. 258 5, 0.007 6 and 0. 004 7 mg·g^-1 , respectively, in which, its content in root is the highest.