Abstract: The CRUD（Chalk Rivers Unidentified Deposit） effect on the fuel rod damage risk under PWR condition Ⅱ accidents has not been considered in the current PCI analysis. In order to clarify the mechanism and influencing level of CRUD on the fuel rod damage, the correlation between the fuel rod damage risk and the CRUD thickness under PWR condition Ⅱ accidents was given from the simulation result of SMART, COPERNIC, CANTAL and THEMIS, series of PCI analysis codes. Research result with thermal analysis illustrates that under the process of wick boiling inside CRUD, the fuel rod damage risk will increase because of the drop of heat transfer coefficient between coolant and fuel cladding. The theoretical and statistical supporting for a more comprehensive methodology for PCI analysis under PWR condition Ⅱ accidents could be obtained via this work.