Abstract: In order to increase emergency repair efficiency and minimize the loss when accidents happen in large-diameter pipelines, it is necessary to develop a pressurized leakage blocking unit that is suitable for this type of pipelines. In the process of emergency repair, however, existing pressurized leakage blocking units are disadvantageous because they are too large and involve excessive amount of earth excavation, long welding duration and low repair efficiency. In this paper, research and development was carried out from the aspects of structural improvement of pressurized leakage blocking units, selection of rare-earth permanent magnets (REPM) and design of connecting mechanisms. The newly developed magnetic-combination pressurized pipeline leakage blocking unit is suitable for leakage blocking and emergency repair of large-diameter pipelines thanks to the introduction of Nd-Fe-B magnets into leakage blocking technologies. It is characterized by simple structure, small size, light weight and convenient operation. Based on this unit, emergency repair time can significantly be shortened, hence emergency repair efficiency can be increased.