Objective: To establish a RP-HPLC method for determination of the related substances in desvenlafaxine succinate. The impurities mainly included 4-(2-dimethylaminoethyl) phenol (impurity A), 4-[2-amino-1-(1-hydroxycyclohexyl) ethyl] phenol (impurity B), 4-[1-(1-hydroxycyclohexyl)-2-(methylamino) ethyl] phenol (impurity C), 2-(1-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N, N-dimethylethanamine oxide (impurity D), 4-[2-(dimethylamino)-1-(1-hydroxycyclohexy) ethyl]-2-({5-[2-(dimethylamino)-1-(1-hydroxycyclohexy) ethyl]-2-hydroxyphenyl}methyl) phenol (impurity E), 4-(1-cyclohexenyl-2-(dimethylamino) ethyl) phenol (impurity F), 1-[2-(dimethylamino)-1-(4-methoxyphenyl) ethyl] cyclohexanol (impurity G), 4-(1-cyclohexyl-2-(dimethylamino) ethyl) phenol (impurity H). Methods: The determination was performed on a Waters Symmetry C18 column (250 mm × 4.6 mm, 5 μm) with the mobile phase consisting of a mixture of 0.05 mol·L-1 phosphate buffer (pH 4.0) and acetonitrile by gradient elution at a flow rate of 1.0 mL·min-1. The column temperature was 30°C, and the detective wavelength was 225 nm. Results: A good linearity was obtained in the measured concentration ranges for desvenlafaxine succinate and 8 impurities (r2 ≥ 0.999 0), and the detection limits (S/N = 3) were 0.60, 0.39, 0.60, 0.58, 0.59, 0.40, 0.61, 0.60 and 0.61 ng for desvenlafaxine succinate, impurity A, impurity B, impurity C, impurity D, impurity E, impurity F, impurity G and impurity H; The content of impurity C was 0.04%-0.05%, the content of impurity E was 0.06%, impurity A, impurity B, impurity D, impurity F, impurity G and impurity H were not detected, and the content of total impurities was 0.10%-0.11%. Conclusion: The established method can be used for determination of the related substances in desvenlafaxine succinate.