Fifteen summer soybean varieties with relative higher and lower yields in mid-south of Hebei province were used for researching on root traits by pot experiment.At 41,65 days after seeding,the root morphological and physiological traits were determined during two years and two location respectively.The RIL population derived from Kefeng 1×Nannong 1138-2 was used to mapping the QTLs of root trait related to yield.Results showed that the increment of root-active-morphological traits(IRRAMT),namely,increment of the products of root reductive activities and root fresh weights,root total lengths,root volumes,respectively,were significant different between two yield types.The IRRAMT could be used for the index of yield.There identified were fore,three,three QTLs located on N6-C2,N20M,N18-K,N14G、N3B1 linkage groups for IRRAW,IRRAL,IRRAV respectively.Each of the traits appeared to have one locus with relatively large effect in comparison with their other loci,and those major ones were located at a same linkage group N6-C2.