Seed length and seed width are an important factor to the soybean yield. So the quantitative trait loci (QTL) location for seed length and seed width could assistant the breeding of soybean. In this study, the QTL underlying seed length and seed width were studied. A recombinant inbred line population of soybeans derived from a cross between the American semi-draft cultivars Charleston and Dongnong 594 were used in 7 environments. The quantitative trait loci underlying seed length, seed width, and seed length/seed width were analyzed by the method of composite interval mapping.