Abstract: The domestic large-diameter valves have been widely used in the 3rd West-to-East Gas Pipeline. However, valve blowing, puffing, dripping and leakage occur frequently, heavily threatening the pipeline operation and maintenance. For oil and gas pipeline engineering constructions, control of valve internal leakage is a top priority in engineering quality control. In this paper, two internal leakage paths of valves are identified in terms of their body structures, quality inspection and construction management on the basis of data statistics and analysis, as well as geographic locations and natural environments, after disassembly experiments are performed on the valves. Considering the specific situations and degrees of the internal leakage, the plugging measures for the two internal leakage paths are made out. Moreover, the considerations are confirmed for the design, production, inspection, transportation and maintenance of valves. In this way, the valve internal leakage is controlled effectively, and the engineering quality is promoted.