Abstract: A method for the determination of 3 double-chain quaternary ammonium salts, including didecyl dimethyl ammonium chloride, octyldecyl dimethyl ammonium chloride, dioctyldimethyl ammonium chloride in compound disinfectant by high performance liquid chromatography combined with differential refractive index detector was proposed. The compound disinfectant sample was diluted by the mobile phase and eluted by Welchrom C₁₈ column as the stationary phase, and the mixed solution (pH 3.5) composed of acetonitrile and 0.01 mol·L^-1 sodium butane sulfonate solution at volume ratio of 70\:30 as the mobile phase. It was shown that linear relationships between the mass concentrations and corresponding peak areas of 3 double-chain quaternary ammonium salts were found in the range of 50-1 000 mg·L^-1, with detection limits (3S/N) in the range of 3.3-5.1 mg·L^-1. Test for recovery was made on the actual sample at 3 concentration levels by standard addition method, giving results in the range of 91.0%-105%, with RSDs (n=6) of the determined values in the range of 1.3%-2.2%. The independent sample t-test was used to compare whether there was significant difference between the proposed method and high performance liquid chromatography combined with evaporative light scattering detector. It was shown that t value and P value of the detection results of the two groups were 1.85 and 0.089, respectively, indicating there was no significant difference.