Abstract: Gas chromatography-mass spectrometry (GC-MS) method was established for trace analysis of the potential genotoxic impurity chlorocyclohexane in trihexyphenidyl hydrochloride bulk drug, utilizing an RXI-5SIL MS column at isothermal temperature of 60 °C for the entire 6-minute run time.The inlet temperature was 180 °C and a split ratio of 10∶1 was used with the injection volume of 1.0 μL.The selective ion monitoring mode was set at m/z 82 for chlorocyclohexane with a detector voltage of 0.3 kV and an ion source temperature of 240 °C.The method was verified with respect to specificity, limit of detection (LOD), limit of quantitation (LOQ), accuracy, precision and robustness.Good linear correlation was achieved with coefficient r of 0.999 9 in the concentration range of 59.72-493 ng/mL.The intra- and inter-day precision was satisfactory (RSD ≤ 5.0%) and robust (RSD ≤ 1.65%).The proposed method in this study can be adequately adopted as a tool for quality assurance of trihexyphenidyl hydrochloride in routine test of potential genotoxic impurity.