The invention provides a silkworm sex-limited marking darkening transformation method. The method includes: hybridizing bred sex-limited silkworm variety A female silkworm moths with the male silkwormmoths of black-striped silkworm to obtain generation F1; back-crossing the female silkworm moths of the generation F1 with the male silkworm moths of the sex-limited silkworm variety A to obtain generation F2, wherein the generation F2 comprises silkworms B with black stripes and common markings, silkworms C with common markings and without black stripes and plain-striped silkworms D; hybridizingfemale silkworm moths in silkworms B with male silkworm moths in silkworms D to obtain generation F3, and repeating the hybridization until the colors of the silkworms of the generation F3 are stabilized at two marking colors, that is to say, the silkworms in generation F3 comprise silkworms E with black stripes and common markings and plain-striped silkworms F; hybridizing female silkworm mothsin silkworms E with male silkworm moths in silkworms F to obtain generation F4, repeating the hybridization until all the silkworms with black stripes and common markings are female silkworms and theplain-striped silkworms are male silkworms. The method has the advantages that female and male silkworms can be identified in the larval phase of the silkworms, breeding cost is lowered, and silkwormegg hybridization rate and variety purity lowering caused by misjudgment is avoided.