The phenomenon of supersonic combustion chamber is very complex, full of shock wave system, expansion wave system. It is related to the supersonic, hypersonic flows in the shock/shock intersection, shock wave and boundary layer interaction, separated flow, fuel flow, as well as the complex structure of vortex structures. In this paper, the calculation of the high-speed flowfield coupled with combustion in an internal flowpath of airbreathing hypersonic vehicle is carried out with two methods: one-dimensional and three-dimensional numerical simulation, and the flow nature and the parameters distribution are shown. The basis theory of one-dimensional flowfield is firstly expounded, then the four one-dimensional models are analyzed and compared. This paper compares literature of determining the core flow area in the one-dimensional flow analysis and makes improvements. According to the static pressure data by Billig’s experiment, all the parameters are calculated using the four models. Then the four models are compared to select a optimal model. The flow field parameters of the extended isolation of the supersonic combustion are computed using the optimal model, and the results are approaching the experiment data. Since the onedimensional numerical simulation only simulates the law of the axial parameters and does not adequately reflect the parameters distribution of the supersonic combustion flowfield, and the two-dimensional calculation can not be completely simulated the fuel injection, the three-dimensional NS equation is used in order to obtain the detailed flowfield parameters. The computing grids of the extended isolation of the supersonic combustion are firstly drawn, and the high-speed flowfield is simulated using the large-scale parallel processor and the software of FLUENT. Eventually the results can reflect the flowpath of the supersonic combustion, and the three-dimensional numerical simulation can make up the short of the one-dimensional models.