Both the pollination control system and genetic distance are major factors in the utilization of crop heterosis.The recessive genic male sterile line (RGMS), 7-7365A (Bnms3ms3ms4ms4), has been widely applied to hybrid seed production because it can generate a completely male sterile population by crossing it with the 7-7365C temporary line (Bnms3ms3rfrf).In this study, the sterile genes of 7-7365A were transferred to the new Brassica napus 7-749 and 7-750 with a high content of subgenomes by backcross breeding.We used the amplified fragment length polymorphism (AFLP) technique combined with bulk segregated analysis (BSA) to identify markers linked to the BnMs4 gene.Twelve AFLP markers linked to the BnMs4 gene were identified.Of them, SA06MG09 and P08MG16 were the closest makers, which were on either side of the gene at a distance of 0.9 cM and 0.8 cM, respectively.Twenty AFLP primer combinations were used to screen the F2, BC1 F3, and BC2F4 populations from the breeding program, and the markers linked to the BnMs3 and BnMs4 genes were used to screen the BC2F4 populations.As a result, we obtained two types of improved sterile lines, 7-749A and 7-750A, and their indexes of subgenomic components (ISG) were 44.2%-49.8% and 20.2%-26.6% , respectively.The combining ability analyses of seed yield character were conducted in the crosses from the three sterile lines and ten restorers within a random block design in three environments for two successive years.The general combining ability (GCA) of the two improved sterile lines were significantly higher than the GCA of 7-7365A in every environment tested.The two improved sterile lines had stability in seed yield, and they will be used in the future for hybrid seed production.