The invention belongs to the field of renewable energy sources and environmental protection and relates to a method for producing ethanol and methane by mixed fermentation of paper-making sludge and monosodium glutamate waste liquid. The method comprises the following steps of: mixing the monosodium glutamate waste liquid and the paper-making sludge according to a dry weight ratio of 3 to 10:100 to obtain a raw material mixture; adding cellulase, nutrient solution and the like into the mixture; adjusting the pH value so that the mixture is acid; inoculating saccharomyces cerevisiae to perform fermentation to produce the ethanol; after the fermentation is finished, distilling to obtain the ethanol; and adding anaerobic digestion inoculation sludge into the distillation remainder to perform anaerobic digestion to produce the methane. The method has the advantages that: the ethanol is produced by synchronous diastatic fermentation without any sterilization operation, the process is simple and the operability is strong; meanwhile, the ethanol and the methane are both produced under an intermediate-temperature condition, so the production condition is mild and the energy consumption is low; and besides, due to the adoption of the mixed fermentation of the paper-making sludge and the monosodium glutamate waste liquid, the living environment of the microorganisms can be improved in terms of trophic structure, the yield of ethanol and methane can be increased, and the harmlessness, reduction and recycling of the two major solid wastes are realized.