Abstract: With the development of the internal high-pressure plugging technologies for oil and gas pipelines, it is necessary to improve the safety and reliability of internal high-pressure plugging device. For this regard, the structural designs of internal plugging devices at home and abroad were investigated in this paper. Then, a structure scheme of single-section double-seal internal plugging device suitable for the oil and gas pipelines with diameter of 508 mm was proposed, and the plugging capacity was theoretically analyzed and calculated according to the designed performance indexes. Finally, the plugging capacity of the newly designed single-section double-seal internal plugging device was simulated by means of finite element simulation analysis method. The simulation analysis result is higher than the theoretical calculation value required by the indexes, indicating that the plugging capacity of the newly designed internal plugging device satisfies design indexes. This study provides a reference for the structural design of single-section double-seal internal plugging device, and plays a certain role in promoting the technical progress and equipment development of the internal high-pressure plugging in China.