Abstract: The characteristics theory and the corresponding calculation methods are classical methods of gas dynamics, which have high computational efficiency in the rotating detonation flow field analysis. The analysis of the rotating detonation flow field is simplified in the wave-fixed reference frame, and the steady-state flow field calculation method is established by using the method of characteristics and the unit processes. The effect of the equivalence ratio and the plenum stagnation conditions on the rotating detonation flow field structure of premixed hydrogen/air, methane/air and octane/air is studied. The calculated results show that the detonation wave height and inclination angle are significantly affected by the equivalence ratio and the stagnation temperature, and decrease as the fuel changing from the small molecule hydrogen to the macromolecular hydrocarbon. The equivalence ratio and the stagnation temperature mainly affect the macroscopic flow field structure by affecting the propagation velocity, height and inclination angle of the detonation wave.