Based on a mechanical seal which is already used in reactor coolant pumps (RCP),an interference fit simulation model is established by ANSYS. End face deformation of the stator/rotor seal ring is calculated. As a result,the mechanical seal’s leakage is available,which is close to the specific operation value. The comparison results between leakages which are calculated by model include interference fit or not illustrated that interference fit has significant influence on structural analysis and should be paid more attention on it. Using this example,the idea and method of ANSYS interference fit analysis is demonstrated.