Abstract: The performance of spent fuel bay（SFB） clean up system is important for both radiation and radwaste reduction.Demineralizer resin is operated adverse conditions facing high levels of hydrogen peroxide generated from radiolysis of water and also direct radiation attack from radioactive colloids in the pool.Resin cross-linked structure will be easily destroyed,because of sulfate ion and purification efficiency rise and decline.This paper,through nuclear resin oxidation stability tests and based on the nuclear power plant application experience,discusses the failure mechanism of resin,and give the purification resin selection principle,in order to improve the purification efficiency and reduce the amount of radioactive spent resin.