The invention relates to a gas disinfectant for silkworms and an application thereof. The gas disinfectant for silkworms is a chlorine-dioxide-containing gas which is generated by reacting raw materials consisting of chlorine dioxide liquor and citric acid liquor in a volume ratio of 1:1. The gas disinfectant disclosed by the invention has the characteristics of a high diffusion rate, uniform distribution, strong penetrability, no residues after disinfection and the like; the chlorine dioxide liquor and the citric acid liquor are combined together for disinfecting air of a silkworm-breeding environment in silkworm-rearing production; the gas disinfectant is simple and convenient, can quickly generate the chlorine-dioxide-containing gas and can disperse the chlorine-dioxide-containing gas to a space including some narrow gaps which need disinfection, and can simultaneously realize all-around disinfection of mulberry leaves, silkworm bodies, a silkworm rearing bed, environment and air, so that the disinfection efficiency is greatly improved. The gas disinfectant disclosed by the invention can be used to effectively control pathogenic microorganisms in the skin-rearing environment to prevent occurrence and spread of silkworm infectious plant diseases, and has disinfection effect which is efficient, safe, broad-spectrum and free of toxic or side effect.