Abstract: Plugging tee is a special form of radial nozzle for cylindrical shell. However, there is no unified standards for its design scheme and strength calculation method, due to its large opening rate and complex stress components at the opening edge. In this paper, some common methods of opening reinforcement calculation for pressure vessel were presented. Taking the 1 422 mm plugging tee as an example, pressure area method, pressure-area stress method and finite element stress analysis method were adopted for reinforcement calculation. Comparison of the calculation results shows that the pressure area method is insufficient in the aspect of safety allowance, and the pressure-area stress method has some problems if ASME BPVC Ⅷ-1-2010 is adopted, but provides the most similar results to the finite element stress analysis method if ASME BPVC Ⅷ-2-2010, which has no limit for opening rate, is adopted. In addition, the calculation in ASME BPVC Ⅷ-1-2010 is simple and convenient, so it should be preferred in the design and calculation of plugging tee.