The influence of flow pattern, leakage location and leakage aperture changes on the flow field and the sound field in horizontal pipelines are studied in this paper. The CFD software is used to simulate the gas-liquid two-phase flow in horizontal pipes. Findings from literature research, it is necessary to study the change of flow field with different parameters in the simulation process. To study the flow field, first, a mathematical model of gas-liquid two-phase flow pipeline leakage established. The flow field parameters of gas-liquid two-phase flow is calculated under different gas&liquid inlet. Then, the fluent is used to solve the flow field, and the appropriate acoustic model is selected to realize the conversion of flow pattern to sound field. Finally, the simulation results are analyzed and verified through experiments. In this paper, we have simulated the change characteristics of the flow field and sound field of different flow pattern, leakage position, aperture size and the sound field, which is helpful to further understand and grasp the location and propagation law of the leakage source.