Preparation method of 3, 3'-diamino sulfobenzide

The invention relates to a preparation method of 3, 3'-diamino sulfobenzide, in particular to a preparation method of the 3, 3'-diamino sulfobenzide, which has simple process, moderate reaction condition, little equipment investment, low cost and easy obtaining of a catalyst, little time consumption as well as high product purity and reaction yield coefficient. The preparation method is mainly realized by taking 3, 3-binitro sulfobenzide as a raw material, taking iron oxide hydroxide as the catalyst and hydrazine hydrate as a hydrogendonor in a saturated low-level fatty alcohol solvent systemand reducing the 3, 3-binitro sulfobenzide into the 3, 3'-diamino sulfobenzide under 60-70 DEG C. The invention has short technological path, can repeatedly and circularly use the catalyst, has littlethree wastes and is especially suitable for the small-batch production of the 3, 3'-diamino sulfobenzide.