Abstract: Under the same constraints,a conventional 2-Dscramjet inlet and a 3-D　sidewall compression scramjet inlet were designed by using the recently developed advanced methodology.The flow field structure and overall performance were studied comparatively and numerically at Ma=4,5,6.The results indicate that,the flow field distortion of 2-D　scramjet inlet was much weaker than that of the sidewall compression scramjet inlet.The mass capture ratio of 2-D　hypersonic inlet was more greatly affected by incoming Mach numbers than that of the sidewall compression inlet.Numerical simulation shows that,the 2-D　inlet was superior to the sidewall compression inlet at the design point,while under off-design points,especially at the starting Mach number,the performance of the sidewall compression inlet was obviously superior to the two-dimensional inlet.Under the equivalent compression state,the drag characteristic of the sidewall compression inlet was superior to that of the two-dimensional inlet,while the lift force of the 2-D　dimensional inlet was greater than that of the sidewall compression inlet.