Gas-liquid mixing is a commonly used technology for oil and gas pipeline transportation, and compared with single-phase pipelines, when a gas-liquid mixing pipeline leaks, the flow is complicated due to the interaction between gas and liquid phases. And among all flow types, segmental plug flow is the most difficult to study. In order to study the control strategy of segment plug flow in the case of unsteady flow multiphase flow in oil and gas pipelines, this paper uses computational fluid dynamics (CFD) to design the control equations and turbulence model, and selects the volume of fluid (VOF) model as the multiphase flow model, so as to analyze the pressure characteristics of the severe segment plug flow through numerical simulation, and based on which, we design the improved PID control system of the segment plug flow, and validate the validity of it. Based on this, an improved PID control system for blocked flow has been designed and its effectiveness has been verified. The results show that the numerical simulation model of unsteady flow in oil and gas pipelines established in this paper can well simulate the changes of various characteristic parameters in the section plug flow condition, and realize the mathematical model description of the pressure characteristics of the section plug flow condition. At the same time, the designed PID control system can effectively attenuate or eliminate the severe segmental plugging flow, control the pressure at the bottom of the riser at a stable value of 71.8 bara, control the pressure at the top of the riser near a stable value of 51 bara, control the mixing density of the flow at the top of the riser at a stable value of 577.2 kg/m3, and control the mass flow rate of the flow at the top of the riser at a stable value of 10.491 kg/s, which indicates that it can help the researchers to realize the pressure characteristics of segmental plugging flow conditions. This shows that it can help researchers to realize numerical simulations of unsteady multiphase flows in oil and gas pipelines and effectively control section plug flows.