Abstract: The three-dimensional flow structure induced by normal shock wave/turbulent boundarylayer interaction in a constant-area rectangular duct at Ma=1.68 is numerically investigated by using the Reynolds Stress Model and k-ω- SST turbulent model. In comparison with SST model, the RSM model resolves secondary flow effects, and therefore a reduced corner separation zone is acquired. This leads to a better match between the experimental data and the RSM results. Under the effect of the wall friction due to viscosity, the shocks of shock train will bifurcate near both top/bottom walls and side walls, and the threedimensional “λ” shock waves are formed at the duct corner. In the position close to the wall, the foreleg shock of the first “λ” shock splits and a new smaller “λ” shock wave is observed.