Redundancy method for pneumatic control system of liquid rocket engine

A redundancy method for a gas control system of a liquid rocket engine comprises the steps that a control gas cylinder is communicated with a control gas circuit after sequentially passing through a control gas pressure reducing valve and a first three-way pipeline, and a downstream controlled valve is controlled; the non-control gas cylinder is communicated with a non-control gas circuit after sequentially passing through a non-control gas pressure reducing valve and a second three-way pipeline; the second three-way pipeline is communicated with the first three-way pipeline through a parallel pipeline, and a one-way conducting electromagnetic valve is arranged in the middle of the parallel pipeline; when the engine is shut down, the electromagnetic valve is opened, and it is guaranteed that the second three-way pipeline is unidirectionally communicated with the first three-way pipeline; the outlet pressure of the control gas pressure reducing valve is not less than the control cavity pressure of the downstre