A reversed phase high performance liquid chromatographic method for the assay of tripchlorolide (T4) in pharmaceutical preparation was developed. The method used a Nucleosil 5 C18 column and a mobile phase of methanol-water (1:1). The column effluent was monitored at 218 nm. T4, triptolide (T0) and 1,4-dimethoxybenzene (IS) could be separated in less than 25 min. The retention times of T0, T4 and IS are 11, 17 and 23 min respectively. The method is very simple and rapid.