A quasi-one-dimensional analytical method with a novel model for precombustion shock train has been proposed to model different modes in the dual-mode scramjet flowfield. The interaction between shock and combustion is modeled by a strength-adaptable model in the isolator, named the "X shock." An iterative procedure is implemented to solve the precombustion shock and the flow properties downstream. The calculation of the combustor is based on a series of governing equations where the effects of area change, friction, and mass injection are included. The release of energy is obtained from a fuel-mixing model or pregiven heat release distributions estimated from experimental results. The numerical results of pressure are compared with the experimental data for validation of the present model. The results show that the quasi-one-dimesional method can be applied to analyze diverse modes in the whole process of the dualmode scramjet combustor. Subscripts in = conditions in the inlet of the isolator max = maximum value min = minimum value 0 = total or stagnation conditions