To improve blast resistance of the rice cytoplasmic male sterile（CMS）line SanxiangA and its maintainer SanxiangB，a PCR-based co-dominant InDel marker CoInDF1R1 was developed to select the broadspectrum and durable blast resistance gene Pi9 in breeding practice. By performing the greenhouse inoculation assay using twenty-eight Magnaporthe oryzae strains isolated from different rice areas in China and abroad， the Pi9 gene donor rice line 75-1-127 showed much higher resistance frequency（85.71%）than that of two acceptor parents SanxiangA and SanxiangB（28.57%）. The Pi9 functional marker CoInDF1R1 produced a 320 bp fragment in 75-1-127 and a ca. 410 bp fragment in both SanxiangA and SamxiangB. A CMS line SanxiangAPi9 and the corresponding maintainer SanxiangB-Pi9 both showing significant blast resistance were obtained by taking advantage of a ten-year consecutive backcross breeding practice and CoInDF1R1-assisted selection. In the natural disease nursery，SanxiangA-Pi9 and SanxiangB-Pi9 as well as the Pi9 donor line showed highlevel blast resistance at the seedling stage，whereas two acceptor parents SanxiangA and SanxiangB remained highly susceptible. Pollen I2-KI staining and field bagged seed-setting assays showed that SanxiangA-Pi9 and SanxiangA with sparse circular abortive pollens under microscope and no self-pollinated seed was obtained. On the contrast，SanxiangB-Pi9 and SanxiangB expressed normal pollen staining reaction and fertility. Furthermore， SanxiangA-Pi9 represented excellent cross-pollination traits，its stigma exsertion rate reached 61.70%. In the field cultivation assay，SanxiangA-Pi9 and SanxiangB-Pi9 showed complete uniformity as their acceptor parents on main agronomic traits，while possessed much more spikelets per plant，thus implying promising yield and heterosis.