Burial depth of marine gas reservoir in Yuanba region surpasses 6500m. There were some problems, such as high drag and torque, high temperature, which proposed higher demands for horizontal well drilling technology. Well Yuanba 272H was the first horizontal well deployed in Yuanba Ⅱ region, and the drilling construction is very difficult. By means of optimization design, advanced borehole trajectory control technology, drag and torque precise forecast analysis, application of advanced HTHP MWD, measuring and controlling problems under high temperature environment was resolved. Drilling fluid resistance to high temperature was used, and properties was adjusted immediately according to stratigraphic characteristics, and the demands of high-temperature stability, cuttings carrying capacity and lubricating property was meet. Through the construction of well Yuanba 272H, a set of drilling technology suit for ultra-deep horizontal well in Yuanba region was formed.