The invention discloses a preparation method for flame-retardant sound-insulating wall cloth, and belongs to the technical field of the wall cloth preparation. The method comprises the following steps: firstly modifying polypropylene by using antimony trioxide and red phosphorus with fire resistance, and wiredrawing the modified polypropylene to be modified polypropylene fibers by a spinneret hole; because the antimony trioxide and red phosphorus do not affect the polypropylene with heat resistance in the heated decomposition process, increasing the release amount of an incombustible gas; extracting plant fibers from bamboos in the alkaline and acidity process, mixing the plant fibers with peach gum and biogas slurry, fermenting to form a fermentation product, decomposing the peach gum tobe macromolecular saccharides with viscidity by using microorganisms in the biogas slurry, and strengthening the cohesiveness of the plant fibers and the modified polypropylene fibers; continuously coating a layer of coating formed by mixing magnesium hydrate and aluminium hydroxide; and co-modifying the magnesium hydrate and aluminium hydroxide by using a titanate coupling agent TMC-201, and further improving the fire resistance of the wall cloth. The preparation method is economic and environmental, and has the extensive application prospect.