OBJECTIVE：To establish the method for the con tent determination of related substances in belinstat. METHODS ： HPLC method was adopted and the principal component self-control comparison method with correction factor was used to calculate the contents of related substances. The determination was performed on ODS-AM column with 1.02％ potassium dihydrogen phosphate buffer （pH value adjusted to 3.5 with phosphoric acid ）-acetonitrile（85∶15，V/V）as mobile phase A ，1.02％ potassium dihydrogen phosphate buffer （pH value adjusted to 3.5 with phosphoric acid ）-acetonitrile（30 ∶ 70，V/V）as mobile phase B （gradient elution ），at the flow rate of 1.0 mL/min. The column temperature was set at 30 ℃，and the detection wavelength was 220 nm. The sample size was 10 μL. RESULTS：The linear ranges of belinstat and impurities A ，D，F，G，H were 0.113-1.693， 0.050-1.496，0.117-1.750，0.098-1.471，0.120-1.799，0.100-1.506 μ g/mL（r≥0.999 7）. The correction factors of the last 5 impurities were 1.0，1.0，1.2，1.5，1.0；the detection limits were 0.250，0.590，0.490，0.600，0.500 ng，respectively. The quantification limits were 0.500，1.170，0.980，1.200，1.000 ng，respectively. The recoveries were 90.18％-111.48％（RSD＝ 1.52％-4.78％，n＝9）. RSDs of stability （100 h）and precision tests were no more than 16％，and the durability was good. Impurities A ，D and H were detected in 3 batches of belinlestat ，the contents were 0.030％-0.038％，0.019％-0.022％ and 0.012％-0.013％，respectively. The contents of other maximum monomer impurities were 0.012％-0.013％ and the total impurities were 0.075％-0.084％. Impurities B ，C，F，G were not detected. CONCLUSIONS ：The method for the content determination of related substances in belinstat has been successfully established ，and the method is accurate and specific.