Six mulberry varieties were selected for feeding young silkworm, Bombyx mori L. These varieties were Morus alba Linn. Var. Iljiros (A), Morus Ihou Koidz. Var. Josaengrok (B), Morus alba Linn. Var. Kearyang-Seoban (C), Morus Ihou Koidz. Var. Nosang (D), Morus alba Linn. Var. Afiluniz (E) and Morus alba Linn. Var. Kokuso-27(G). During the 4^th and 5^th larvae instar of silkworm instar, nutritional were tested, data were collected on the biomass of larvae and cocoons for 6 treatments on ingesta, digesta, excreta, approximate digestibility (AD), reference ratio (RR), consumption index (CI), relative growth rate (RGR), respiration (R) and metabolic rate (MR), efficiency conversion of ingesta (ECI) and digesta (ECD) for larva, cocoon, and shell. Further, the ingesta and digesta required for producing one gram of cocoon and shell (I/g and D/g). Characters of young instars duration (YID), fifth duration (FID), total larval period (TLD), cocooning percentage (CP), pupation ratio (PR), sex ratio (SR), number of cocoons/liter (C/L), fresh cocoon weight (FCW), fresh cocoon shell weight (FCSW), fresh pupa weight (FPW), fresh cocoon shell ratio (FCSR) and silk productivity (SP) for female and male. In addition to length of silk filament (FL), weight of silk filament (FW), size of reeled thread (denier; FS) and silk ratio (SR) were investigated.