Abstract: Violent vibration and noise symptoms have been found in a nuclear piping system, which is caused by the cavitation after a throttle orifice. The research and engineering modification of this issue are presented in this paper. Intensive investigation with numerical and experimental methodologies has been made to find the root cause of the malfunction, and then the modification ways are proposed based on the conclusions of root cause analysis. Field investigation and evaluation after system modification have shown great suppression of the vibration and noise symptoms, while the system function and structure integrity have been validated to meet the requirement of original design code, which demonstrates that the system modifi- cation issuccessful. Moreover, a “numerical simulation priority” approach is introduced in the research work and the application of this approach has significantly reduced the time and cost of the whole project.