Riserless drilling is usually used in deep sea drilling. For change of the drill bit or the bottom hole assembly , logging or dealing with the incident in the hole, it is necessary to trip out the drilling string and then get it back into the original hole, and this process is called “well reentry”. Because the drilling vessel is separated from the submarine wellhead by water for several kilometers, it is unstable with the drill string swinging due to the waves and ocean currents. It is not easy to reenter the original hole. Through extensive investigations, this article introducesseveral common reentry drilling technologies at home and abroad in detail, compares the advantages and disadvantages of different technologies, optimizes the underwater television reentry drilling technology. The design approach for deepsea drilling well reentry technology is put forward, laying the foundation for development of the prototype and reentry process.