The results of three out-combinations indicated that the wild silkworm could be utilized to attain breeds with short larval instar period and fine filament size as bridge materials in domestic silkworm breeding and to enrich gene pool of the domestic silkworm. The domestic parent should be of superior cocoon and filament quality in outbreeding.The selection was even more efficient when started from F 4 thereafter.The line should be set up as early as possible according to the segregation of qualitative characters and backcrossed with domestic silkworms while making use of relationships between characters and paying attentions to recessive characters to speed up breeding procedure.