The sulphate content of a system increases when strong-acid cationic exchange resins leak into a system or when sulphonic acid groups on the resin organic chain detach. To solve this problem, a dynamic cycle method was used in dissolution experiments of several resins under H2O2 or residual chlorine conditions. Results show that after performing dynamic cycle experiments for 120 hours under oxidizing environments, the SO42− and total organic carbon (TOC) released by four kinds of resins increased with time, contrary to their release velocity. The quantity of released SO42− increased as the oxidizing ability of oxidants was enhanced. Results showed that the quantity and velocity of released SO42− under residual chlorine condition were larger than those under H2O2 condition. Data analysis of SO42− and TOC released from the four kinds of resins by the dynamic cycle experiment revealed that the strength of oxidation resistance of the four resins were as follows: 650C > 1500H > S200 > SP112H.