The invention discloses a preparation process of 2-naphthylamine-3,6,8-trisulfonic acid. The preparation process of 2-naphthylamine-3,6,8-trisulfonic acid comprises the following steps: 1, adding 2-isonaphthol into sulfuric acid for carrying out sulfonation reaction, and thus obtaining a sulfonated product after the reaction is completed; 2, adding the sulfonated product into the mixed solution of ammonium hydroxide and sodium chloride for salting out, and thus obtaining salt mixture and mother solution; 3, under the existence of ammonolysis catalyst, carrying out the ammonolysis reaction between the salt mixture and the ammonium hydroxide, and after the reaction is completed, acidizing, dehydrating and drying to obtain amide; and 4, adding the amide into fuming sulphuric acid for carrying out sulfonation reaction, and after the reaction is completed, obtaining the 2-naphthylamine-3,6,8-trisulfonic acid by aftertreatment. According to the preparation process, a one-step method is employed for salting-out and one-time ammoniating, so that the operating steps are simple, the problem of wastewater treatment in traditional technology is solved, meanwhile the unit consumption of 2-isonaphthol, as the material, is reduced, and the production cost is also reduced.