Abstract: Objective：To develop a liquid chromatograph-mass spectrometer（LC-MS） method for the determination of related substances in Benazepril hydrochloride tablets. Methods：The separation was performed on a Waters SunFire C18 column(2.1 mm×150 mm，5 μm) at a flow rate of 0.2 mL·min-1 and an injection volume of 20 μL， by a gradient elution using 0.1 mol·L-1 ammonium acetate solution(acetic acid adjusted pH to 3.0) as mobile phase A and methanol as mobile phase B. The detection wavelength was set at 240 nm. The column temperature was 35 ℃. MS scan range was 100-1 000 amu. Results：The proposed method was used to detect the related substances in Benazepril hydrochloride tablets from different pharmaceutical manufactures. The chemical structures of related substances were analyzed by LC-MS.Conclusion：The developed method is appropriate for determination of related substances in Benazepril hydrochloride tablets.