The invention belongs to the biology engineering technical field, and relates to a method for preparing indigo by conversing indole through phenol-degrading bacteria. The invention is characterized in that the phenol-degrading microbial strain capable of effectively catalyzing indole to synthesize indigo is employed, and is Pseudomonas monteilii QM, and the preservation number is CGMCC No.5054; when the biotransformation reaction is carried out, the cell dry weight concentration of the Pseudomonas monteilii QM bacterium in a reaction solution is 0.1-10g / L, the indole concentration is 25-200mg / L, under temperature of 20-40 DEG C, the shaking table rotating speed is controlled with 50-300r / min, and the oscillation reaction lasts for 1-8 hours. The condition of the biotransformation reaction is mild, the product concentration reaches as high as 42.5mg / L, the production period is short, the cost is low, the extraction step is simple, the production step is clean, and the method is suitable for industrial production and application.