The flowfield in liquid fuel purge method and the effect of parameters on purging process are analyzed using one-dimensional numerical simulation. The combustor length, total pressure of oxidizer, the width of propellant region from the ignition point to the upstream side and back pressure are taken as the parameters. The purge process occupies a large part of the entire cycle and the back flow of burned gas which has linear relationship with the time required for the burned gas needs to be suppressed. The maximum back flow distance of burned gas depends on the pressure ratio of burned gas to oxidizer flow and is minimized when the oxidizer flow is choked and the propellant does not exist upstream from the ignition point at the ignition time. For realizing the high frequency operation, it is desired to make the flow choked by increasing total pressure of oxidizer and decreasing back pressure and to shorten the width of propellant region upstream from the ignition point at the ignition time.