Objective:To rapidly identify the chemical components in a traditional Chinese herb Xiaochaihu decoction by high performance liquid chromatography-time of flight mass spectrometry (HPLC-TOF/MS).Methods:An Agilent ZORBAX SB-C18 column (100 mm×3.0 mm,3.5 μm) was used for rapid separation and identification of chemical components in Xiaochaihu decoction,with a mobile phase of methanol and 0.1% formic acid aqueous solvent in gradient elution.The flow rate was 0.6 ml/min and the injection volume was 4 μl.The detector was time-of-flight mass spectrometer with an ESI ion source.Scanning mass range was m/z 200-1 500.Results:Thirty-eight chemical compounds were identified from Xiaochaihu decoction in one run.Conclusion:Thirty-eight chemical compounds have been identified in Xiaochaihu decoction by HPLC-TOF/MS in one run,which paves a way for further understanding the metabolism and mechanism of the chemical compounds in Xiaochaihu decoction.