Improvement of the blast resistance in rice varieties by marker-assisted backcrossing (MABC) approach has been regarded as one of the most effective tools. In this study, a comprehensive investigation of the genotypes and phenotypes of improved ‘BC15’ rice lines harboring two blast resistant genes, Pik-h and Piz-5, was carried out. Particularly, the BC3F3 populations exhibited high resistance to the blast isolates under greenhouse condition. The presence of Pik-h and Piz-5 genes and the genetic background of these individuals were then validated and confirmed by PCR technique with a collection of specific SSR markers. As a result, three individuals, A2.1.15.3.3, A2.1.19.9.8 and A2.1.26.3.12, were obtained to expand the populations in the fields. We found that the whole three lines that shared similar agronomical traits with the original BC15 rice variety, resistance to blast disease (scored < 3). Among them, the A2.1.15.3.3 line was selected to develop a promising line for further studies. Taken together, our study could provide a basic understanding of the improvement of stress tolerance in rice varieties by the MABC approach.