In the production process of offshore platforms, because the oil well produced fluid is a mixture of natural gas, crude oil, water, mineral impurities and other substances, it cannot be directly exported, and a certain process is required before it can be exported, stored or sold. The three-phase separator, as a relatively mature equipment in the process, has been widely used in the production of offshore platforms. Among them, the gravity sedimentation three-phase separator has been widely used as the basic separation equipment. Due to the existence of a large number of risers on offshore platforms, unstable conditions such as slug flow may occur in the fluid in the pipes. In order to ensure stable production, a certain control theory needs to be used to control the production process of the three-phase separator. As a mature and stable control theory, PID control has been widely used in on-site production. Therefore, the simulation of the process flow and related parameter settings of the gravity sedimentation three-phase separator and the corresponding pressure PID controller and the liquid level PID controller has certain guiding significance for the on-site production process. In this paper, through an in-depth analysis of the relevant field data drawings of an offshore platform, the corresponding production process model is established, and the offshore platform is used to simulate the production process of the offshore platform for the related process flow of oil and gas processing. It verifies that the PID controller is guaranteed in production. An important role in stabilizing production. And based on the simulation of basic operating conditions, the unstable operating conditions are designed to further verify and compare the control effect of PID control on the fluctuation of incoming flow, and analyze the response of PID control for the unstable incoming flow of different frequencies and different gas-liquid ratios. characteristic. In addition, on the basis of process simulation, the selection of various characteristic parameters (proportional gain, integral time, derivative time) of the PID control system has been studied in depth and sensitivity analysis has been completed. For different controlled parameters such as pressure, hydraulic According to the response characteristics of each parameter, the corresponding PID parameter recommended settings are proposed.