Abstract: It is necessary to solve the problems of mud surface collapse and drilling tool reentry in ocean drilling operation. Reentry cone is a special device for ocean drilling reentry, which can be deployed in two ways: Free-Fall Funnel （FFF） and Reentry Cone and Casing （RECC）. The FFF is a temporary reentry wellhead designed to support reentry in a short term, while the RECC can be used as a permanent subsea device to support drilling reentry in the current and future voyaging. In this paper, we introduce the principle, key tools, and process of RECC, and summarize our first shallow sea test, in which the feasibility of simultaneous deployment process of reentry cone and casing was verified, and the functionality of our newly-developed running tool and underreamer-while-drilling was tested. The shortcomings of the running tool in sealing structure were found. This study lays a theoretical and practical foundation for further research on drilling reentry and drilling-in casing technology in complex deep-sea scenarios.