A simple structure square lobed mixer with high mixing efficiency and low resistance was designed to turbofan by pass flow with ram bypass flow thoroughly in turbine based combined cycle engine hyperburner. Numerical simulation of square lobed mixer and comparative analysis with conventional mixer were made; the results indicate that square lobed mixer with high mixing efficiency and low resistance of the streamwise vortices of daisy lobed mixer. Numerical simulation results of various mixer structure parameters' influence on mixing characteristics show that expansion angle dominates the thermal mixing efficiency

and the export height of the mixer has little effect on it. The square lobed mixer has the characteristics of high mixing efficiency and low resistance when the wavelength ratio is 1.0.