OBJECTIVE: To establish an HPLC method for the determination of the contents of the related substances in metoclopramide.METHODS: The sample was separated on C18 column with the mobile phase consisted of acetonitrile-0.02 mol?L-1 phosphonic acid solution(19∶81) at a flow rate of 1.0 mL?min-1.The detection wavelength was set at 275 nm;the column temperature was kept under room temperature and the injected volume was 20 ?L.The contents of the related substances in metoclopramide were computed by self-control method of main constituent.RESULTS: Under the above described chromatographic conditions,metoclopramide was completely separated from its impurities.A good linearity between impurities' peak area and metoclopramide(contrast solution) concentration was achieved when the concentrations of impurities were over the range of 0.05%～4.0%.The lowest detectable limit of metoclopramide was 0.3 ng,and the contents of the related substances were all less than 0.26%.CONCLUSION: The method is convenient,accurate,sensitive and,specific,and it can be used for the determination of the related substances in metoclopramide.