Pi9 is a broad-spectrum rice blast resistance gene which is located at the In this study, a specific inner genic molecular marker Pi9–a was developed based on the sequence of the Pi9 gene, and was employed for improving the blast resistance of 8 receptor indica rice lines (FengyuanB, Ⅱ32B, Tianlongxiang103, Xiangfeng187, Minghui63, Lunhui422, R747 and 25H003) through marker-assisted selection (MAS) and back-cross breeding. Pi9–a showed obvious and stable polymorphisms between the donor line of Pi9, 75–1–127 and 8 receptor lines except Xiangfeng187. The individuals from 4 BC1F1 populations were genotyped and phenotyped, and the result showed that the selection efficiency using Pi9–a was 100%.