The wireline logging operation cost can be reduced effectively in open sea. However, due to the influence of ultra-deep water and ultra-shallow environment, it is faced with difficulties and challenges such as the swaying of cable logging instruments caused by shallow water surge, the difficulty of "entering hole" of cable testing instruments and the hidden danger of underground safety in open sea. In this case, the 20 "casing is inserted to seal off the shallow swell to form an effective sealing. Make full use of the underwater robot "underwater eyes" and auxiliary role to ensure the success of the instrument "into the hole"; The speed of the instrument is strictly controlled, and the dual monitoring mode of "ROV underwater + platform control panel" is adopted to ensure the safety of operation. A pilot test was carried out in an ultra-deep and ultra-shallow exploration well in Qiongdongnan Basin, South China Sea, and several wireline logging operations were successfully carried out, detailed logging data were obtained, and operating costs were greatly reduced. This operation practice has accumulated valuable experience for subsequent ultra-deep open sea operations, and provided a powerful technical solution for offshore oil and gas exploration and development to increase reserves and production, reduce costs and increase efficiency.