1, 4-dihydroxyanthraquinone is oxidized with sulfuric acid and manganese dioxide, then condensed with aniline in the presence of boric acid, and then sulfonated with sodium bisulfite, and then salted out, filtered, and dried. The product is prepared by the process. The product is a uniform black powder with a black appearance, the color light is similar to the standard product (blue gray), the strength is the standard product 100±3 (points), the water insoluble impurity content ≤ 1.5% moisture content ≤ 5%, the fineness (through 80 mesh sieve residue content) ≤ 5%, and the dyeing fastness on the wool fabric conforms to the standard product (sun drying, water soaking, sweat soaking, cooking, ironing, etc. are countless levels 5, soaping, carbonization, and friction are grade 4-5.) Raw material consumption (kg/t)1,4-dihydroxyanthraquinone 410 aniline 360 sulfuric acid 3100 fuming sulfuric acid 4200 manganese dioxide 380 boric acid 120 sodium bisulfite 40 yuan sodium sodium sulfate 45 sodium bicarbonate 4 bleaching liquid 2 refined salt 1400