Abstract: According to the mixing feature of two supersonic flow streams,a new design method of supersonic mixer of sloped lobed shape was presented based on the concept of lobed nozzle.The principle of design is to achieve high efficient mixing at low flow loss.A finite volume method was used to solve the three dimensional compressible viscous Navier-Stokes equations,and the turbulence model was k-ε model.The numerical simulation for under-expansion,optimum-expansion and over-expansion situation has been completed.The calculated results show that the vortex and saddle-shape shock wave caused by the jet can improve the mixing efficiency at a special angle between the top of the inside passage and outside passage.The flow condition of the two supersonic flow streams in the mixer meets the design requirements.The result of under-expansion,optimum-expansion is satisfactory,but the result of over-expansion is not good enough.