Abstract: Semi-submersible crane vessel (SSCV) is a kind of column stabilized unit which consists of deck box, column and pontoons. The main functions of this kind of vessel are heavy lifting and J-lay pipe-laying. SSCV's seakeeping performance and weather windows are much better than normal vessel type. There is a lot of equipment on the vessel with a big power request, with the total power normally beyond 60 MW, and 4 even 6 engine rooms and more than 8 thrusters are needed. Due to the high cost and the technical difficulty, SSCVs in the world are very few, and the core technology has been monopolized by several foreign companies. In order to continuously improve the capacity of China's deepwater marine equipment and break the monopoly of foreign companies, COOEC is conducting the early research of SSCV. To provide reference for further research of domestic technicians, we summarize the current status of SSCV in the world, and introduce the main characteristics of this vessel.