The general aim of selection in animal breeding is to acquire new generation of animals, which under future economic conditions of production system are more efficient than the present generation. In selection index method, genetic trend of important traits is directed based on their weights in economic efficiency of production system to acquire maximum improvement in economic merit (Mirhosseini et al., 2005). Silkworm commercial egg is produced by crossing between Japanese and Chinese origin parent stocks. There are three steps in the cycle of egg production including GGP (great grand parent), GP (grand parent) and P (parent stock). Breeding programs along with high selection pressure are used only in GGP lines which are typically much smaller in size than other stocks. The objective of this study was to evaluate effect of six generations of index selection in the GGP lines on performance of commercial silkworm hybrids.