C.I. 34905(Acid Brown 75) was synthesized by the multi coupling to resorcinol with three different diazonium salts made from H-acid, picramic acid and pnitroaniline. Dye synthesis was carried out in four different routes and the results were discussed with the stabilities of these salts and the change of reactivity of resorcinol with pH. The dyes synthesized by the flour different routes showed different color characteristics, which was caused by by-products. When the stabilities of the these salts and the reactivity of resorcinol were considered, a coupling route in order of H-acid, Picramic acid and p-nitroaniline to resorcinol was the best course of preparing the C.1. 34905.