Abstract: It is difficult to maintain high performance over a wide range of Mach numbers for a hypersonic inlet.An osculating curved cone waverider inlet is designed and the design point of the inlet is optimized to obtain high performance with Mach numbers ranging from 4.5 to 6.From the numerical simulation and experiment results,it is found that the inlet mass flow capture ratio and the engine thrust can be efficiently improved by adjusting shock on lip Mach Number from 6 to 5.5,while the inlet can be guaranteed to be self-started by optimizing the inlet sweepback an-gle of the sidewalls.The experiment shows that the designed scramjet engine performance is im-proved under off-design conditions.