To investigate the genetic mechanism of Al-tolerance in soybean, a recombinant inbred line population (RIL) with 184 F2:7:11 lines derived from the cross of Kefeng No.1 × Nannong 1138-2 (Al-tolerant × Al-sensitive) were tested in pot experiment with sand culture medium in net room in Nanjing. Four traits, i.e. plant height, number of leaves, shoot dry weight and root dry weight at seedling stage, were evaluated and used to calculate the average membership index (FAi) as the indicator of Al-tolerance. The composite interval mapping (CIM) under WinQTL Cartographer v. 2.5 detected five QTLs (i.e. qFAi-1, qFAi- 2, qFAi-3, qFAi-4 and qFAi-5), explaining 5.20%-9.07% of the total phenotypic variation individually. While with the multiple interval mapping (MIM) of the same software, five QTLs (qFAi-1, qFAi-5, qFAi-6, qFAi-7, and qFAi-8) explaining 5.7%-24.60% of the total phenotypic variation individually were mapped. Here qFAi-1 and qFAi-5 were detected by both CIM and MIM with the locations in a same ?anking marker region, GMKF046-GMKF080 on B1 and satt278-sat_95 on L, respectively. While qFAi-2 under CIM and qFAi-6 under MIM both on D1b2 were located in neighboring regions with their confidence intervals overlapped and might be the same locus. Segregation analysis under major gene plus polygene inheritance model showed that Al-tolerance was controlled by two major genes (h2mg = 33.05%) plus polygenes (h2pg = 52.73%). Both QTL mapping and segregation analysis confirmed two QTLs responsible for Al-tolerance with relatively low heritability, and there might be a third QTL, confounded with the polygenes in segregation analysis. To investigate the genetic mechanism of Al-tolerance in soybean, a recombinant inbred line population (RIL) with 184 F2: 7: 11 lines derived from the cross of Kefeng No.1 × Nannong 1138-2 (Al-tolerant × Al-sensitive ) were tested in pot experiment with sand culture medium in net room in Nanjing. Four traits, ie plant height, number of leaves, shoot dry weight and root dry weight at seedling stage, were evaluated and used to calculate the average membership index (FAi ) as the indicator of Al-tolerance. The composite interval mapping (CIM) under WinQTL Cartographer v. 2.5 detected five QTLs (ie qFAi-1, qFAi-2, qFAi-3, qFAi-4 and qFAi-5) % -9.07% of the total phenotypic variation individually. While with the multiple interval mapping (MIM) of the same software, five QTLs (qFAi-1, qFAi-5, qFAi-6, qFAi-7, and qFAi-8) 5.7% -24.60% of the total phenotypic variation individually were mapped. Here qFAi-1 and qFAi-5 were detected by both CIM and MIM with the location while qFAi-2 under CIM and qFAi-6 under MIM both on D1b2 were located in neighboring regions with their confidence intervals overlapped and might The same locus. Segregation analysis under major gene plus polygene inheritance model showed that Al-tolerance was controlled by two major genes (h2mg = 33.05%) plus polygenes (h2pg = 52.73%). Both QTL mapping and segregation analysis confirmed two QTLs responsible for Al-tolerance with relatively low heritability, and there might be a third QTL, confounded with the polygenes in segregation analysis.