The effect of pressure gradient on separation of supersonic compressible boundary layer is studied at two different Mach numbers of 5.0 and 6.0. Moreover, the study of constant suction effect at different locations is performed for flow at Mach number 5.0. The non-similar boundary layer equations for steady compressible flow have been solved with a potential flow velocity distribution corresponding to power law edge Mach number variation. In this study, the changes in Prandtl number and the specific heat with temperature are considered. The resulting conclusion show that the higher adverse pressure gradient is less affected by a constant suction than the lower one.