Abstract: A method for the determination of 25 volatile organic compounds (VOCs) including halohydrocarbons, benzene series, chlorobenzene compounds and etc. in groundwater samples by purge and trap sampling-gas chromatography-mass spectrometry was developed. Selected ion monitoring (SIM) scan and full scan modes were used for qualitative analysis and the internal standard method for quantitative analysis. The detection limits of the method for the VOCs were 0.10~0.20 μg/L. The average recoveries of the method were 83.9%~104.5% with precision of 3.23%~10.1%RSD (n=7). The method provides the advantages of low detection limits, good precision, high efficiency and is suitable for routine analysis of VOCs in groundwater samples.