It is obtained by closed loop and sulfonation of benzoyl benzoic acid. Operation Example 998kg of 20% fuming sulfuric acid and 574kg of 65% fuming sulfuric acid are added to the pot (the concentration of fuming sulfuric acid after mixing is 36.5%). At a temperature lower than 90 ℃, 595kg of benzoylbenzoic acid is added, 670kg of recovered anthraquinone is added, the temperature is raised to 145 ℃, and the temperature is kept for 4 hours. After sulfonation, the sulfonate was diluted in the previous batch of lotion and kept at 100 ℃ for 2 hours. Filter and wash with 100 ℃ hot water to make it neutral. The filtrate and part of the concentrated washing liquid are sent to the neutralization pot, and the light washing liquid is reserved for diluting the next batch of sulfonates. The filter cake is recycled anthraquinone, dried, and used for the next batch of vulcanization. Control the neutralization operation and post-treatment conditions to obtain anthraquinone-2-sulfonic acid or its sodium salt. The specific operation steps are as follows: the filtrate of anthraquinone is added into the neutralization pot, diluted with ice water, the temperature is reduced to 30 ℃ and the relative density is 1.09, and 17-20% ammonia water is added to neutralize to pH 7. Cold to 25 ℃, keep the temperature for 0.5h, filter, wash with a small amount of ice water, blow dry, filter cake to obtain 650kg(100%) of anthraquinone 2-ammonium sulfonate. The total yield was 75% (based on anthraquinone).