The invention discloses a method for producing sodium saccharin. The method comprises the following steps: with phthalic anhydride as a raw material, preparing a sodium saccharin solution with baume degree of 25-40 Be at 60 DEG C through an amidation reaction, an esterification reaction, a diazotization reaction, a substitution reaction, a chlorination reaction, an ammonolysis reaction and a neutralization reaction, decoloring, filtering, concentrating, crystallizing, centrifugally drying and drying to obtain a finished product of sodium saccharin, wherein the ammonolysis reaction comprises: with liquid ammonia as a raw material, reacting liquid ammonia with o-sulfonylchloride methylbenzoate obtained in the chlorination reaction to generate o-sulfonamide methylbenzoate. The production method can be used for shortening the process route, reducing the production procedures, lowering the production cost, as well as reducing the ammonia nitrogen emission in production wastewater, the emission of 1 moL NH4<+> can be reduced in each production of 1 moL sodium saccharin, so that the ammonia nitrogen emission in the production wastewater can be decreased by 50% to benefit environmental protection.