Biodegradation of azo dyes usually started in anaerobic conditions with a reductive cleavage of the azo bond. Some reductive processes take place also in presence of molecular oxygen, a one-step azo dye degrading process had been investigated. A microbial consortium able to degrade Acid red B in aerobic and microaerophilic conditions had been selected. The optimal decolorization rate of Acid red B had been completely degraded under the condition of shaking for 14h and resting for 22h. Different concentrations of trace metal had been studied to determine the best condition for biodegradation after 36h inoculation. With the optimal concentration of ten trace metals, the Acid red B decolorizing efficiency was increased by Corynebacterium variabile.