Abstract: 1.0 g of the water-soluble fertilizer sample was taken, and 80 mL of water was added. The mixture was dissolved ultrasonically for 10 min, and the obtained solution was made its volume up to 100 mL and then filtered through 0.22 μm filtration membrane. A mixture of 0.4% (φ) triethylamine solution (adjusting pH to 6.0 with acetic acid) and acetonitrile in the volume ratio of 90:10 was used to separate 3 quaternary ammonium salt plant growth regulators, including choline chloride, chlormequat and mepiquat chloride, from the filtrate on CNWSIL SCX COLUMN. The separated target compounds were detected by evaporation light scattering detector. The evaporation temperature and atomization temperature were set to 80℃, atomization gas flow was 1.8 L·min^-1, and gain value was 8. As shown by the results, linear relationships between the log values of mass concentration and corresponding peak area of 3 quaternary ammonium salt plant growth regulators were found in the same range of 20-200 mg·L^-1, with the same detection limits (3S/N) of 4 mg·L^-1. Recovery test was carried out with blank samples, giving results in the range of 95.9%-105%, with RSDs (n=6) of the determined values in the range of 1.2%-2.8%. The method was applied for the analysis of actual samples, and choline chloride, chlormequat and mepiquat chloride were all detected to a certain extent.