Abstract: Aiming at the service conditions and ch aracteristics of the pipe for supporting offshore drilling platform pile column, theФ355.6 mm×65 mm large-sized, extra-heavy-wall NV E550 seamless steel pipe as per Specification DNV-OS-B101 is developed successfully by means of researches concerning relevant design of chemical composition, melting process, rolling process, heat treatment process and applicable welding process, etc.Relevant test results show that the said pipe is in possession of high strength and excellent low-temperature impact toughness, homogeneous microstructure, and good weldability, having been satisfactory to the customized requirements for design and application.The pipe as developed has been DNV-certisfied.