Abstract: It is possible to define a fixed geometry hydrocarbon fuel dual-mode scramjet operating in a large Mach number range (between Ma=3 to 8).The efficient design of an inlet is crucial to the successful operations of the scramjet.The goal in the design of any hypersonic inlet is to define a minimum weight geometry that provides an efficient compression process,generates low drag,produces nearly uniform flow entering the combustor,and provides these characteristics over a wide range of flight and scramjet operating conditions.A two-dimensional hypersonic forebody/inlet of mixed external and internal compression with plane lip and wedged lip is designed in this paper by using constant shock angle method and constant shock intensity method.The design point of the designed forebody/inlet is determined to be Ma=6,H=25 km.The effects of temperature and shock/boundary-layer interaction are considered in the design.The design and off-design performance and flow field of several types of designed forebody/inlet are calculated and compared.The comparison results indicate,at lower flight speed,the starting performance and total pressure recovery coefficient of forebody/inlet with wedge lip are better than that with plane lip.At high flight speed,the forebody/inlet with plane lip shows higher pressure ratio and lower cowl drag,but the forebody/inlet with wedge lip exhibits high total pressure recovery coefficient and high cowl drag.Moreover,the performance of inlet designed by constant shock angle method or constant shock intensity method is similar.The presented method is applicable to the preliminary scheme choice of hypersonic forebody/inlet.