Male sterility plays an important role component of heterosis utilization in Brassica napus L.The B.napus line,7-7365ABC, is a recessive epistatic genic male sterile (REGMS) three-line system.The phenotype of 7-7365A with two pairs of recessive duplicate male sterile genes (Bnms3 and Bnms4) and one pair of dominant epistatic inhibitor gene (BnRfRf) is male sterility, 7-7365 B with one pair of heterozygous gene BnMs3, only this locus is different from 7-7365A, is male fertility, and 7-7365C with the recessive homozygous genotypes at three loci shows male fertility.Histological studies leading to male sterility, expression regulation pathways and the role of ABA in the anther development of REGMS were reported here.In the male sterile line 7-7365A, tapetum cells and microspore mother cells separation was effected, which leading to failure of microspores release.The activity of polygalacturonase (PG) and the expression of the pectin methylesterase (AT3g06830) gene were significantly down regulated.Nine genes were down regulated in 7-7365A compared with 7-7365B and 7-7365C including tapetum specially expressed A3, A9, Ms1 genes and ABA responding gene Kin1.Exceptionality, gene AT5G09480.1 was down regulated in 7-7365B and 7-7365A compared with 7-7365C.ABA concentration in 7-7365B was significantly higher than that in 7-7365A and 7-7365C, respectively.We proposed that the REGMS is controlled by the main pathway of male sterile metabolism positively regulated by the BnMs3 gene and the supplementary pathway negatively regulated by the BnRf gene.ABA might control the genes expression for cell separation during early anther development in the main pathway.