Abstract: The conventional welding process for pipeline. Taking the GMAW of the X80 and X110 linepipe steels as an example, the co-authors of the paper have a discussion on the main problems involving welding of high-grade linepipe steels, and a comparative analysis with respect to the difference between the mechanical properties of the welding joints respectively resulting from the single-wire welding process and the said dual-wire welding process as applied to welding of the X80 linepipe steel. And the work principle and advantages of the dual-wire welding process are elaborated. Also described in the paper is the successful application of the said dual-wire welding process to the construction of a certain submarine pipeline. The operation practice leads to such a conclusion that in case of site boxig of the high-grade linepipe steel, the employment of the dual-wire welding process will not only improve both the welding quality and operation efficiency, but also reduce the degree of the steel structural coursing and softening of the heat-effected area under the welding so as to get the mechanical properties of the weld joint improved.