With simple molecular structure and thorough utilization of microorganisms, methanol solves the problem of large sludge increment and difficult to reduce quantification caused by adding carbon sources such as sodium acetate and starch, reduces the burden of sludge treatment in sewage treatment plants, and saves operating costs of enterprises. As the external carbon source of the sewage treatment plant, methanol, on the one hand, solves the environmental problem that the effluent of the sewage treatment biological system can not reach the standard stably when the carbon source of the influent is insufficient; On the other hand, it solves the safety problems of flammable and explosive pure methanol, which is harmful to human health.