Abstract: There are phenomena such as interphase energy consumption and interphase mass transfer in the process of gas-liquid mixed transportation, which can afect the flow state of medium and the operating parameters of pipelines. Meanwhile, the composition of gas and liquid is also varying continuously. Thus, LedaFlow software was used to conduct the steady-state simulation of a real gas-liquid mixed transportation pipeline. Then, the simulation results of pipeline parameters obtained by the physical property model and component tracking model were analyzed comparatively to verify the reliability of component tracking method. On this basis, transient simulation was performed for the pipeline to analyze the variation rule of liquid composition and to predict the phase variation of gas and liquid. According to the results, the fluid in the pipeline is liquefied and the molar flow of gas decreases along the line. Therefore, the transient flow in the pipeline is a process of continuous liquefaction of gas. In the steady-state simulation, the LedaFlow phase equilibrium calculation method could be adopted to accurately determine the phase variation during flowing on principle that the flow proportion of various phases should be same as the distribution of gas and liquid under the condition of rest. Generally, the research results could provide theoretical basis for the prediction of phase variation rule and improve the accuracy of flow safety evaluation of gas-liquid mixed transportation pipeline.