The recombinant inbred line (RIL) population, NJRIKY with 184 families derived from a cross Kefeng No.1 x Nannong1138-2 was used in mapping QTLs of root weight of soybean. Based on the linkage map constructed by Wang, with the software Cartographer V. 1.21 of the composite interval mapping procedure, three QTLs of root weight were mapped on N3-B1 and N6-C2 linkage group. The left telomere distance of rw1 was 66.31cM on N3-B1 linkage group, and those of rw2 and rw3 were 169.91cM and 179.71 cM, respectively, on N6-C2 linkage group. The former was located in A520T approximately ACCCAGO5 and the latter were overlapped with OPW13 and ACGCATO6, respectively. Their LOD values were 10.34,4.01 and 3.15, respectively. The QTLs of the root weight explained 26.3%,9.2% and 6.8% of the total variation, and their additive effects were -0.514,-0.303 and -0.260, respectively.