Abstract: The groundwater samples are pretreated respectively by means of both the liquid-liquid extraction and the C₁₈ membrane disk extraction, analyzed with the GS/MS. The recovery and precision experiment are both conducted to compare the two pre-treatment methods. The recovery of the liquid-liquid extraction with standard samples are generally smaller than 65％, while those of the later with that all vary from 70% to 120%. The relative standard deviations of the liquid-liquid extraction are all less than 30%, while those of the C₁₈membrane disk extraction are less than 20%. In the recovery experiment spiked with standard samples, The results show that the C₁₈membrane disk extraction is optimal. The groundwater samples are analyzed and 63 organic compounds are detected.