Abstract:300 meter deep water jacket is widely used in the South China Sea, however, due to the large overall height and compartment capacity, there are significant changes in jacket upending status and hook force during offshore installation, which affects the safety and stability of the upending process. In order to solve this problem, it is urgent to optimize the flooding and venting system and upending design. This paper takes a deep-water jacket as an example, introduces the flooding and venting system line arrangement and controlled upending scheme, and completes upending process numerical simulation. During offshore operation, the jacket is up-righted according to the upending and flooding sequence, and precise control is achieved by monitoring the compartment pressure to reverse the flooded water amount. The measured data and numerical simulation results are close. Compared with conventional upending plan, the control of compartment flooded water is achieved, and the jacket status during jacket upending process is stable. The research in this paper indicates that the controlled upending design can meet the goal of jacket upending precise control, reduce the risk of offshore installation, and related technologies can be further promoted to conventional jackets.