Abstract: Pipeline plugging is a critical technology in pipeline emergency maintenance. As a key component in the plugging machine, the structure of plugging device directly impacts the pipeline plugging quality. In allusion to the defects that traditional suspended plugging device can hardly plug successfully at one time, a two-stage plugging device is proposed inthis paper. The new device has the function of sweeping the cuttings and residues in pipeline and ensures the rear plugging cup plugs reliably, realizing the goal of one-time successful plugging. Static mechnics analysis on the structure of plugging device and the plugging capacity analysis of plugging cup were conducted. The results show that for a pipeline with adiameter of 324 mm and a medium pressure of 6.4 MPa, the designed two-stage plugging device has a plugging capacity of9.186 MPa, meeting the demands of the pressure difference of 6.4 MPa, leaving a redundant capacity of 40%. The plugging device can plug the pipeline successfully at one time, enhancing work efficiency and improving the safety of pipeline plugging.