Abstract: In order to study the dynamic characteristics of liquid rocket engine injectors,theoretical analysis has been carried out for the plane orifice and centrifugal injectors."Frequency Method" was used for the numerical simulation of the injector dynamics.The results show that with the increase of pulse frequency,the flux swing of the plane orifice and centrifugal injectors decreases and the phase shift increases.With the increase of pressure,the flux swing increases and the phase shift decreases.Under the same condition,with the increase of the plane orifice injector's length or the geometric characteristics of centrifugal injectors,the swing decreases and the phase shift increases.With the increase of the spout length of centrifugal injectors,the phase shift increases while the swing is not affected remarkably.These results agree well with foreign investigations and establish the basis for further study.