Abstract: A method was developed for simultaneous detection of 34 volatile organic compounds (VOCs) such as hexachlorobutadiene, pentachloroethane, hexachloroethane, epichlorohydrin in groundwater by gas chromatography-mass spectrometry（GC/MS） with purge and trap sampling. Isotope-labeled toluene-d8 and 1,2-dichlorobenzene-d4 were used as the internal standard for the quantitative analysis. The detection limits the target compounds are 0.01—0.09 μg/L. The recovery rates are 97.0%—107% with precision of 1.04%—7.6% (RSD, n=7). The method provides the advantages of lower detection limits, good precision， and which is suitable for the determination of trace VOCs in groundwater.