Abstract: In this study, we used the BC₄F₂ population carrying Pi1 and Pi9 disease resistance genes as materials, and used molecular marker-assisted selection（MAS）to complete the construction of the BC₅F₅ strain and carried out the identification of the seedling blast inoculation and natural identification in field under different ecological environments. The results showed that the seedling blast disease of Dalixixiang was grade 7, while the disease grade of the improved strains was grade 2 to 6.The leaf blast grades of Dalixixiang in the two disease nurseries of Meitan and Liping were 8 and 7, and the panicle blast was 9 grades with high sensitivity, and its comprehensive resistance index was 8.4 with the performance of high sensitivity to blast. The disease grade of leaf blast in the diseased nursery was 1 to 7, and the incidence rate of ear blast was grade 5 to 9, showing sensitivity and high sensitivity, but the loss rate of ear blast was lighter, compared with the control Dalixixiang grade 8 ear blast, reduced by 3 to 7 grades.The resistance of the improved lines obtained by molecular marker assisted selection was improved to varying degrees compared with the original parent Dalixixiang, which clarified the difference of rice blast resistance level of the improved lines in different ecological areas, and screened out a number of new rice germplasms for breeding.