Abstract: To develop an LC-MS method for the separation and identification of the related substances in cinacalcet hydrochloride. The separation was carried out on a Thermo BDS Hypersil C₁₈ column(100 mm×4. 6 mm, 2. 4 μm)with mobile phase consisting of 0. 1% ammonium acetate buffer-acetonitrile(93∶7)(A)and acetonitrile(B)by gradient elution. The related substances were identified by electrospray positive ionization high resolution TOF/MS and MS/MS, and verified further through reference substances. Cinacalcet hydrochloride and itsrelated substances were separated under the established LC-MS condition. Ten related substances were detected and identified to be one starting material, one intermediate, four synthetic by-products and five degradation products. It showed that the LC-MS method was useful for separating and identifying the related substances in cinacalcet hydrochloride. And the results obtained are valuable for cinacalcet hydrochloride manufacturing process control and quality assurance.