Abstract: An analytical method has been developed for simultaneous determination of cyromazine and metabolite melamine in green vegetables using a high performance liquid chromatograph (HPLC) coupled with an ultraviolet detector. Fresh green vegetable samples were freeze-dried, homogenized and subjected to extraction in solution containing 95% methanol and 5% aqueous ammonia assisted with ultrasonics. The extracts were concentrated and purified through centrifugalization, rotary evaporation and solid phase extraction, and quantified using a high performance liquid chromatography-ultraviolet detector. It used an Agilent NH₂ column as chromatographic column for separation, solution consisting of 90% acetonitrile and 10% water as carrier with a flow rate of 1 mL•min^-1 and worked with a wavelength of 214 nm. It was found that the standard curves of cyromazine and melamine in the range of 0.05-10 mg•L^-1 showed a good linear relationship with their peak areas with correlation coefficients not less than 0.9995，and the recovery rate of cyromazine and melamine at fortified levels of 0.2-4.0 mg•kg^-1 varied in the range of 81.26%-87.69% and 78.24%-82.33% with relative standard deviation being 2.75%-6.18% and 3.99%-6.67%, respectively. The limit of quantification (LOQs) was 11.30 μg•kg^-1 for cyromazine and 20.38 μg•kg^-1 for melamine. This method is saimple, sensitive and suitable for determination of cyromazine and melamine in green vegetables.