The molecular adsorption of triazine molecule on MgO (001) surface is reported. The ab-initio pseudopotential method and classical molecular dynamics method are used. The first step is to construct a stable structure for one of triazine derivatives (6-ethylamino-2,4-dithioxo-1,3,5-triazine) and MgO surface by the ab-initio method. The equilibrium geometry of triazine molecule agrees well with experimental data. MgO (001) surface energy also confirms that MgO can be calculated with accuracy. After locating these stable structures on virtual space, the second step is to clarify the adsorption site with the classical MD method. On ground of the data from second stage, the last stage is to optimize the adsorbate / substrate system in order to calculate adsorption energy of triazine / MgO interface. The adsorption energy indicates that adsorption in triazine / MgO interface does not occur.