Abstract: During the generation of the thin bed on the containment sump Strainer, the particular debris and the fiber debris with the small size will pass though the strainer and go into the Safety Injection System（RIS）/ Containment Spray System（EAS） flow path. The debris effect on the downstream equipment should be evaluated according to the requirement of the nuclear supervisory authorities. The general method which recommended by evaluation document WCAP-16406 is used in QINSHAN Phase II Extension Project, the calculation and analysis for the blockage and wear evaluations on the downstream effect（ex-core） in PWR are performed.