Abstract: Briefed in the paper is the trial manufacture of JCOE linepipe by Julong Steel Tube Co., Ltd. with X120 linepipe steel as made by Baoshan Iron ＆ Steel Co., Ltd. The study focuses on such aspects as change of the mechanical properties of the X120 steel plate, the forming characteristics, weldability and softening of the heat affected zone（HAZ）of JCOE, the comparative testing with rectangular and round tensile test pieces and the influences by different welding material proportions and welding thermal input on hardness, strength and toughness of the weld joint;Comparative analysis between X100 steel and X120 steel is conducted. Proposals about using round tensile test piece for X120 steel linepipe, and drafting the standards of linepipe steels and steel linepipes are put forward.