Abstract: This experiment deals With the Studies on degummibng loes of cocoon shell of Boabyx mari in terms of heredity and breeding ,and the results showed that there were differences between the various voltines,varieties and male and female silkworms among the same variety.There was no uniform tendency for the cotelation between the degumming loss of cocoon shell and whole cocoon weight,cocoon shell weight and cocoon shell ratio According to the estimation by Heymen model,the pararameters of degumming lossS of cocoon shell were D=1.8344.H1=0.2793,H2=0.2690.F=0.0798;in the besedicery cemponents of degumming loss of cocoon shell.additive componeat was the major one;ist derminant effect was controled by an iacomplese dorminat,major gene or by a group of them;its generalized heretability was 91.16%.while its special one was 82.21%.There was a significant difference between its general combining ability and apecial conbinging ability.Generally,it appeared to be negative to heterosis.Through the systemic hreeding and hybridisation in the selection test of degumming loss of cocoon,it was known that selection was effective,And the more idealistic method was to use the latter oae