Abstract: A high performance liquid chromatography- evaporative light scattering detection method for separation and determination of L-citrulline in Trichosanthis Fructus was established. The analytical column was Agilent ZORBAX SB-Aq ( 250mm × 4.6mm i.d., 5 μm) .The mobile phase was water, and the flow rate was 1.0mL /min.The sample was determined by an evaporative light scattering detector.The temperature of drift tube was kept at 115℃ and the flow rate of atmosphere was 3.2L /min.The result showed that under the optimized conditions, the logarithm correlation between peak area and the concentration of L-citrulline was in a good linearity. The calibration curve had good linearity in the range of 0.05 ～ 0.75mg /mL, the detection limit of L-citrulline was 12.9 μg /mL, and the average recovery was 98.36% ( n = 5, RSD = 1.77% ) . The method was applied in the detection of L-citrulline in Trichosanthis Fructus, and the result revealed that the content was about 0.1mg /g. The method is a convenient, rapid and effective method for qualitatively analysis of L-citrulline in Trichosanthis Fructus.