The invention relates to the technical field of pharmaceutical analysis, in particular to a reversed-phase high-performance liquid chromatography detection method for related substances of doxylamine succinate and discloses an RT-HPLC detection method for the related substances of doxylamine succinate. The RT-HPLC detection method comprises the following steps of preparing an analyzing solution, setting chromatographic conditions and carrying out measurement on a machine. By means of the RT-HPLC detection method, various related impurities in a doxylamine succinate solution can be effectively measured, and separation of doxylamine succinate characteristic peaks and the related impurities in a spectrogram is especially achieved. Thus, it is ensured that the quality of products is controllable.