A novel temporary plugging tool has been developed to address the delayed retrieval of fracturing isolation systems during the completion of casing branch wells in offshore oilfields, where compromised pressure sustainability leads to prolonged tool retention and subsequent operational inefficiencies during completion operations. This study presents the tool's design principles, structural configuration, and mechanical analysis. The tool's key parameters, including its size, were determined through static finite element analysis (FEA) of its rupture disc, with a focus on its pressure bearing capacity and crushing load. A functional relationship between rupture disc thickness, rupture pressure, and temperature coefficient was established. Theoretical and experimental results show that the tool can withstand 35 MPa pressure and its rupture disc will fragment into particles smaller than 5×5×5 mm³ under a 12-ton impact load, enabling efficient discharge from the wellbore. These findings satisfy the technical requirements for the completion of cased branch wellbores in offshore oilfields and highlight the tool's potential for broader application. © Published under licence by IOP Publishing Ltd.