A high performance liquid chromatography (HPLC) to analyze main ingredient hexanitrostilbene (HNS) and the main impurity hexanitrobibenzyl (HNBB) was established. The method was carried out on a Hypersil ODS2 column (250 mm×4.6 mm, 5 μm) using acetonitrile-water (56/44, V/V) as the mobile phase at a flow rate of 0.70 mL·min^-1, and determined by a UV-visible detector at the wavelength of 226 nm. The column temperature was 25 ℃ and the injection volume was 10 μL. Results show that under the optimized chromatographic conditions, the calibration curves of HNS and HNBB have good linearity within the mass concentrations of 5-100 mg·L^-1 and 2-50 mg·L^-1, and the linear correlation coefficient r is greater than 0.999. The detection limits for HNS and HNBB were 0.60 mg·L^-1 and 0.31 mg·L^-1, respectively, and the quantification limits for the two were 2.00 mg·L^-1 and 1.02 mg·L^-1. The spiked recoveries are 99.60%-100.39% with the relative standard deviations (RSDs) between 1.63% and 2.07%. The method has wide linear range, high sensitivity and good reproducibility, and the results are accurate and reliable. The method can be used for the determination of the related substances in the product of HNS, and can meet the demand of the analysis of actual samples.