Abstract: A method was developed for simultaneous detection of more than 20 volatile organic compounds (VOCs) including halogenated hydrocarbons, benzene series compounds, aromatic hydrocarbons and chlorinated benzenes in groundwater by gas chromatography-mass spectrometry with purge and trap sampling. The experimental conditions of purge and trap sampling and gas chromatography-mass spectrometric determination were optimized. The detection limits of the method for the volatile organic compounds were 0.03~0.28 μg/L. The recovery rates were 88.8%~111.0% with precision of 2.21%~5.31%RSD (n=7). The results show that the method is sensitive, accurate and suitable for the determination of trace VOCs in groundwater.