The major dominant fluoride-endurance (Dfe) gene was introduced into the commercial varieties by crossing and pedigree selection to breed silkworm races that could normally develop in the area that polluted by fluoride. After backcrossed for two generations, the Dfe gene was made homozygous, and individuals with good economic characters were selected to generate next generation. After 8 generations of selection, their characters became stable, and the silkworm variety which is resistant to fluoride, Huayuan${ imes}$Dongsheng, for spring rearing were bred.