A field-reversed configuration (FRC) plasma is a high-beta elongated compact toroid only with a poloidal field. Since the plasma torus does not link with confinement coil and vacuum vessel, the FRC can be translated from the formation region to confinement region along the external guide field. In this work, the effects of particle, flux and energy supply to the FRC due to the interaction with background neutral particles has been investigated. Translating an FRC plasma through a neutral gas background is equivalent to the injection of neutral beam end-on into the FRC. The experiments were performed on NUCTE-III and NUCTE-III/T. Due to the effects of back ground particle injection during translation process, the loss rate of particle, flux and energy were reduced.