Abstract: This report takes CPR1000 unit with AFA3 G fuel assembly as the research object, and analyzes the physical characteristics and power distribution of normal fuel assembly and damaged fuel assembly after repairment. It can be found that the effect on the fuel assembly reactivity is about-0.03% for the fuel assembly replaced with a stainless steel rod, and the effect can be ignored. The relative power of fuel rods near the stainless steel rod increases about 5.6%. The stainless steel rod replaced in the fuel assembly has effect on the relative power of fuel assembly about 0.1372% to 0.2698%, on burnup about 0.11%, core moderator temperature coefficient about 2%, and these effects can be ignored. The stainless steel rod replaced in the fuel assembly has no effect on the reactor core power peak factor, core critical boron concentration, core shutdown margin, fuel assembly outlet moderator temperature and core outlet coolant temperature.