Gas field A in the South China Sea is developed using subsea production system, and its multiphase well fluid is tied back via subsea pipeline to the nearby integrated platform for processing. In the later stage of development, slug flow occurs periodically due to big fluctuation in various physical parameters, affecting the normal operation of the gas field. As a first step, it is confirmed that the multiphase well fluid transport system is a typical downdip pipe leading to a vertical riser, and the slug flow demonstrates the characteristics of severe slugging. By analyzing the causes of severe slugging and the effect of changes of actual operating parameters, the critical natural gas flowrate envelop of severe slugging is defined. After comparing the commonly used control methods on slug management, the flow control method is selected. The practical verification of flow control method is carried out using modelling software LedaFlow as the software is found to be feasible for multiphase flow simulation application. The flow control method effectively mitigates the generation of severe slugging in subsea multiphase flowlines, stabilizes the operation of gas processing system on the integrated platform, and provides best practices to support similar severe slugging control issues in the future. It can be promoted for application in other subsea gas field developments as an effective method for severe slugging control.