Abstract: The method to calculate the crack open displacement for circumference and axis through-wall cracks is introduced, and the method to predict the leakage based on Henry homogeneous and non-equilibrium flow model are presented. The method above is implemented by computer code, and comparison study between the test result from public literatures and calculate result is performed. The results show that the method can predict the crack open displacement and leakage effectively and be used for the LBB crack leak evaluation. It should be noted that the method is not a precise approach and some margin should be included in the application.