Soybean aphid (SA: Aphis glycines Matsumura) is one of the most serious pests of soybean [Glycine max (L.) Merr.] worldwide. A single dominant gene was found to control SA resistance in soybean line P746, which exhibits antibiosis resistance. This study aimed to define the location of the SA resistance gene in P746. A F2:3 mapping population, including 312 individuals, was created based on the cross of P746 and ‘Dongnong 47’.