When using pressure pipeline for measuring high⁃temperature pulsating pressure in aircraft engines, high⁃temperature condensed water may cause a state of "gas mixed with liquid" in the pressure pipeline, and using traditional dynamic models of gas medium pressure pipeline for analysis may result in significant errors. In response to this issue, a transfer function of the pressure pipeline under the condition of "gas mixed with liquid" was established based on a compressible fluid pressure pipeline system model. Pressure pipelines of the same length but different inner diameters were selected, and experimental research was conducted under different gas⁃liquid mixing states by adjusting pressure and gas⁃liquid ratio. The relationship between the dynamic characteristics of the pressure pipeline and gas⁃liquid ratio was obtained, and the differentiated features of the dynamic characteristics of the pressure pipeline after gas⁃liquid mixing under different pipe diameters were obtained. This lays the foundation for the subsequent research on the dynamic characteristics of the pressure pipeline under other complex medium conditions, and provides technical reference for improving the accuracy of dynamic pressure testing of aviation engines.