Abstract: The theoretical analysis of the aerodynamic characteristics of high Mach number air-breathing engines is very important for the design and optimization of scramjet or oblique detonation engines. However, due to the varying incoming flow conditions and the complexity of the flow dynamics inside the engines, establishing a satisfactory theoretical model is very difficult. In this paper, firstly, the aerodynamic characteristics of scramjet engines were theoretically analyzed by using CJ detonation theory and some general regulations were obtained. The analysis results are in good agreement with the experimental results. Then, the aerodynamic design principles for oblique detonation engines were put forward based on these theoretical analysis results. Finally, an oblique detonation engine was designed according to these aerodynamic design principles. Two-dimensional numerical simulations were conducted to simulate its combustion flow field. The numerical results demonstrate that steady combustion flow field can be obtained in oblique detonation engines at high flight Mach numbers.