Abstract: S-triazine is an important chemical intermediate. Melamine belongs to s-triazine, which has been widely used as an additive in the food industry. To study the stable isotope labeling method of heterocyclic triazine compounds and its application, one step synthesis of melamine-d₆ was achieved with a yield of 30% (calculate in ND₄OD), which started from ND₄OD by the reaction with cyanuric chloride. According to the exchange mechanism of H/D, the feasibility and the necessary conditions were discussed for applying deuterium labeled compounds in isotope dilution mass spectrometry method.