To estimate and compare the response to selection of quantitative traits in the three commercial pure lines (32, 104 and 110) of silkworm, records and response to the choice of three successive generations were analyzed. According to existing records, for each of these three lines, a choice group was formed; its individuals have average cocoon weight higher than above-mentioned average in their colony. In each of these three lines, another similar colony was formed. Intercourse within the group over next three generations, without re-selection acts, took place and the economic characteristics of each choice were recorded, and respond to each trait, from the average difference in trait in selection and control groups over the previous generation, in every line separation, trait and group, over three consecutive generations were measured. Results from this study showed that selection in based colony based on the weight of cocoon, improved nine traits of these twenty-seven traits, simultaneously in all three commercial lines 32, 104, 110 of silkworm and comparison in the response to selection of three Lines also showed that the difference in response to the selection of these three lines, statistically, for the five traits, is meaningful (p<0.05). In line 32, the highest increase in trait selection resulted in cocoon weight of ten 10000 larvae (412.6 g), in line 104, for weight trait of the whole best cocoon weight (64.77 g), good (77.64 g) and in line 110 for the trait number of hatched larvae was (68.04 larvae). By comparing the response to the choice of above three lines, the trait of number of hatched eggs statistically have meaningful difference. Only in the trait of number of un-fertilized eggs simultaneously, we have observed reduction in all three lines 32, 104 and 110 (i.e. improvement of selection). Considering this, the most reduction of trait rate resulted in this study included in line 32, trait of the number of un-fertilized eggs (- 9.33) in line 104, trait of the number of un-hatched eggs (-4.33) and in line 110, trait of the number of unhatched eggs (-6.13).
