Abstract: The method of headspace-gas chromatography (HS-GC) for the determination of trichloromethane and carbon tetrachloride in water was improved. The equilibrium temperature and time were optimized. The influence of different solvents on standard working solution preparation was investigated, and the different preparation modes of working curves were compared. The results showed that the optimal equilibrium temperature and time were 50 ℃ and 35 min, respectively. When the methanol standard working solution was used instead of pure water, and the standard working solution was injected into the pre-sealed headspace bottle with micro injection needle, all the linear relationship of trichloromethane and carbon tetrachloride were good in a wide range of mass concentration (1~100 μg/L and 0.1~10 μg/L, respectively), and all the correlation coefficient were above 0.999. The limits of detection were 0.027 μg/L for trichloromethane and 0.001 4 μg/L for carbon tetrachloride. The recoveries were 98.3%~103.0% and 94.3%~105.0%, respectively, and relative standard deviations were 0.76%~1.23% and 1.96%~2.47%, respectively. The above results indicated that the HS-GC method is accurate, convenient and has a wider linear range, which is suitable for the analysis of bulk samples of environmental and drinking water.