The invention discloses a rocket liquid oxygen pump filling system, a frequency converter used for flow control of a liquid oxygen pump and a parameter setting method of the frequency converter. The rocket liquid oxygen pump filling system comprises a liquid oxygen pump set and the frequency converter, wherein the frequency converter is used for controlling the filling flow of the liquid oxygen pump. The frequency converter used for flow control of the liquid oxygen pump has precise speed and torque control capacity, meets the requirements for quick step response to refilling before launching, and in addition, has a flexible software configuration function so as to be adapted to local and remote control. The rotation speed energy of the pump is adjusted through control over the output frequency of the frequency converter, and finally the purpose of adjusting the flow of the pump is achieved. The type of the converter is reasonably selected and parameter control of the frequency converter is achieved, so that realization of flow control is guaranteed.