The invention discloses a synthetic method of a dimethyl terephthalate crystal compound (I) with the following chemical formula (I); the formula (I) is as shown in the specification/description. The synthetic method of the crystal compound (I) is carried out by weighing 0.4085g (0.002 mol) of 7, 7, 8, 8-tetracyan benzoquinone bismethane and 0.1225g (0.0005 mol) of manganese(II) acetate tetrahydrate in a round bottom flask; using absolute methanol (about 40 ml) as solvent; after performing the heating backflow reaction for 48 hours, thermally filtering and naturally volatilizing to obtain a crystal.