Abstract: A theoretical model is established to find out why the peak heat flux arises near the reattachment point in hypersonic compression ramp flow and how to predict the location of peak flux.Firstly,the compressible oblique stagnation flow model is set up to describe the nature of flow near reattachment point.Secondly,the approximate solutions of this model reveal that there is a minimum thickness of the boundary layer nearby the reattachment point.Correspondingly,the semi-analytical and semi-numerical method for estimating the location and the magnitude of peak heat flux is presented.Finally,present results are verified by the numerical results,and the extended applications of our theories are discussed.