Abstract: An experiment was done in order to comparison of response to selection in three commercial pure lines of silkworm in spring and autumn seasons. Base population in each line consists of two selective and randomly groups. Selective group to each of the studied lines, superior 40 cocoon male and 40 cocoon female based on single cocoon weight after single recording of the three cocoon weight traits, cocoon shell weight and cocoon shell percentage of the population was selected 3P and another random mating were given. Random group (control) related to each of the studied lines, 40 male cocoon and 40 female cocoons randomly selected without any recording of the mentioned traits among 3P population had been gathered and crossed. In the first generation of the 40 produced larvae eggs categories in each group of each line, 8 categories with hatched percentage and suitable fertility for breeding were hatched. Thus each group consisted of 8 families in each line of brothers and sisters (with a parent). All the first generation, data files consist of 2400 records for each of three traits (800 records per line). Finally among the 8 families per group in each line 40 male cocoons and 40 female cocoons were crossed randomly to produce 40 larvae eggs categories of next generation. Breeding process and producing row data in second generation or 2p and third generation or p was done as the same as the first generation. All data files in all lines contain 7680 records from each of the three traits were studied (2560 records in each line). It should be noted that only selected population in all lines was done just in vase population and all crossing in nest generations were carried out randomly. According to information available to separate spring and fall seasons, the effects of data were separated and the response to selection separately for each season, were recorded and saved in the computer. Separation of effects in spring and fall seasons and compare responses to a choice of three lines of the above actions seaso effect showed that spring effects on three traits of 27 trait and autumn effect on four traits of these traits was significant statistically. Individual selection performance comparisons in base population of above three commercial lines based on cocoon weight and response to selected three lines for 27 traits examined in this study showed that spring effect on three traits of 27 studied traits is significant and the autumn on the four traits have significant effects. Spring effect on three traits in the pupae vitality percentage in middle cocoons, larvae duration and the un-hatched eggs number, the autumn on four traits was significant effects. Spring effect on three traits of pupae vitality percentage in middle cocoon, larvae duration and un-hatched eggs number was significant. Autumn effect on three traits of pupae vitality percentage in best cocoon, best cocoon percentage, middle cocoon percentage and un-hatched eggs number was significant.