Abstract: The cement technology of the underwater wellhead system of the floating drilling rig is faced with the following technical problems: how to set the casing plugs, how to choose the setting locations, how to release the rubber plugs and how to adapt to underwater wellhead systems. In order to solve these problems, subsea release cementing technology was developed after underwater wellhead systems were analyzed in terms of structures and operational principles and floating drilling rigs were investigated and applied in field. They carried out cementing by using intermediate casing and the production casing of the floating drilling rig. In this paper, the principle of the process, the components of the tools, the possible risk points, the process optimization and the development trend are analyzed, and the technical preparation, operation steps and application effects of the field application were illustrated. It was demonstrated that the subsea release cementing technology was characterized by strong operability, good continuity and high stability, and it could meet the drilling requirements of floating drilling rigs and solve the problems encountered in the process of underwater wellhead cementing.