To broaden the genetic basis and overcome the yield plateau in Asian cultivated rice, the exploitation and utilization of favorable alleles from rice species with the AA genome has become important and urgent in modern breeding programs. Four different interspecific populations were used to detect quantitative trait locus(QTL) for seed length, including a BC4F2 population derived from Oryza glumaepatula crossed with Dianjingyou 1(a japonica cultivar), a BC4F2 population derived from O. nivara crossed with Dianjingyou 1, a BC7F1 population derived from a cross between O. longistaminata and RD23(an indica cultivar), and a BC8F1 population derived from a cross between O. glaberrima and Dianjingyou 1. The QTLs for seed length in four different populations were termed as SL-3a, SL-3b, SL-3c and SL-3d, respectively. They had good collinearity and accounted for 49% to 60% of the phenotypic variations. Sequencing data indicated that four QTLs were different alleles of GS3 which were responsible for the seed length variation between O. sativa and its four AA genome relatives. These results will be valuable for confirming the evolution of GS3 and also be helpful for rice breeding. To broaden the genetic basis and overcome the yield plateau in Asian cultivated rice, the exploitation and utilization of favorable alleles from rice species with the AA genome has become important and urgent in modern breeding programs. Four different interspecific populations were used to detect quantitative trait locus (QTL) for seed length, including a BC4F2 population derived from Oryza glumaepatula crossed with Dianjingyou 1 (a japonica cultivar), a BC4F2 population derived from O. nivara crossed with Dianjingyou 1, a BC7F1 population derived from a cross between O. longistaminata and RD23 (an indica cultivar), and a BC8F1 population derived from a cross between O. glaberrima and Dianjingyou 1. The QTLs for seed length in four different populations were termed as SL-3a, SL-3b, SL-3c and SL-3d , respectively. They had good collinearity and accounted for 49% to 60% of the phenotypic variations. Sequencing data indicated that four QTLs were different alleles of GS3 which were responsibl e for the seed length variation between O. sativa and its four AA genome relatives. These results will be valuable for confirming the evolution of GS3 and also be helpful for rice breeding.