The invention belongs to the field of analytical chemistry, and in particular relates to a method for separating and measuring levocetirizine hydrochloride and its genotoxic impurity E by HPLC. The chromatographic column adopted in the method is filled with octadecyl bonded silica gel, and is eluted with a mixed mobile phase of potassium dihydrogen phosphate, methanol and / or acetonitrile, and enters a detector for detection. The method is reversed-phase high-performance liquid chromatography, which can realize the separation and detection of levocetirizine hydrochloride and its genotoxic impurity E at the same time, and has excellent separation performance and durability, is simple and feasible, has good reproducibility, and is highly efficient. Fast, tailing factor and theoretical number of steps can achieve very good results, and can effectively determine the content of genotoxic impurity E in levocetirizine hydrochloride, with strong specificity.