Abstract: Based on the stress distribution in a hollow cylinder, the relation between the radial pressure and the interference tolerance is determined. Based on the maximum shear stress theory, theoretical expressions of the stress intensity of penetration and hole are given. For instance, the stress distribution of the penetration of the reactor pressure vessel is computed by theoretical expressions and finite element method. The computational results show that theoretical expressions of the penetration satisfy the requirement of engineering precision, and provide technical support for the design of the penetration of reactor pressure vessels.