Abstract: In the HPLC analysis of bendamustine hydrochloride, two related substances(IMP01 and IMP02)were detected. These two related substances were identified by LC-MS/MS and their structural confirmation was unambiguously carried out by synthesis followed by characterization using Q-TOF/MS and NMR. Based on the spectral data, related substances IMP01 and IMP02 were characterized as 4-(1-methyl-5-morpholino-1H-benzo［d］imidazol-2-yl)butyric acid hydrochloride and 4-1-methyl-5-［(2-chloroethyl)(2-hydroxyethyl)amino］-1H-benzo［d］imidazol-2-yl) butyric acid hydrochloride, respectively. Bendamustine hydrochloride and its related substances were separated under the established LC-MS condition. HPLC is a useful method for the determination of the related substances in bendamustine hydrochloride. Results obtained are valuable for its manufacturing process and quality control.