Abstract: A method of determination of Trifluralin in water by gas chromatography has been established. Trifluralin in water was extracted by the liquid-liquid extraction (LLE) and solid phase extraction (SPE) respectively. The LLE method is easy to operate and saves time. The SPE method can realize automatic processing and save labor. These two pre-treatment methods have their own advantages. Then the enriched organic phase was separated on a HP-5 column, and an electron capture detector (ECD) was used in the measurement. The result showed that when the mass concentration of Trifluralin in water was in the range of 0.05~1.0 μg/L, the correlation coefficient of the regression equation of working curves was higher than 0.999. The detection limit (3 S/N) was 0.02 μg/L. The recovery and precision were tested under two different concentration levels. The recovery and relative standard deviation were obtained in the range of 84.0%~98.0% and 3.0%~5.8%, respectively.