Abstract: The frequency characteristics of a gas generator cycle liquid oxygen / liquid hydrogen(LOX/LH₂) rocket engine system was analyzed numerically using matrix transform method.One-dimensional distributed parameter models were used to describe the pipelines and other components of the engine system.The models were transformed to frequency domains and described as transmission matrixes.According to the connecting relationship of the engine elements,the engine system was divided into several modules with corresponding transmission matrixes.The linear equations of engine system,which relate system variables and perturbations,were constituted from module transmission matrixes.The frequency characteristics of the system variables were thus obtained from these equations.For the purpose of validation,the frequency characteristics of a staged combustion cycle LOX/LH2 rocket engine system was analyzed as well to show the difference with the one of the gas generator cycle liquid rocket engine system.