Investigation on the fluoride-resistance of silkworm,Bombyx mori,and estimation of the corelatlonship between the fluoride-resistance and the other economic characters had been conducted.These can provide the scientific basis for the breeding of anti-fluoride races.The resistance to the fluoride-poisoning is strengthened with the growth of silkworm larvae,that is,4th instar>3rd instar>2nd instar.The resistant ability of F1 hybrids of the strong fluoride-resistance crossing groups was in between that of the parents'.For the Fl of the weak fluoride-resistance crossing groups,their resistance expressed was higher than their parents'.The resistance of different varieties was significantly different due to the various concentrations of fluoride.The andi-fluoride and the anti-DNV characters wen in significant positive corelation.But there were no such corelation to the cocoon quality,and the content of Ca and Mg ions in the larvae blood.