According to the typical characteristics of ultra deepwater semi-submersible drilling platform, the overall planning method of the dual well operation system is given. The analysis of hook load, pipe setback load and types of derrick and hoisting system, riser storage, blow out preventer (BOP) stack storage and processing system is mainly focused on. The main loads and technical parameters of the system are confirmed. An arrangement plan of the drill floor, moon pool and pipe rack area is proposed. A general design of the operation system is formed, which provides the design basis for ultra deepwater semi-submersible drilling platform.