Treatment of styrene-divinylbenzene sulfonated cation exchangers with a small amount of thionyl chloride prior to reaction with chlorosulfonic acid significantly facilitates the production of sulfochlorides from polymeric sulfonic acids and their salts. Polymeric sulfochlorides were synthesized by sequential treatment of gel and macroporous styrene-divinylbenzene cation exchangers in Na and H forms with thionyl chloride and chlorosulfonic acid. Transformation of these sulfochlorides into sulfamides via reaction with ammonia, followed by treatment with gaseous chlorine, yielded polymeric sodium N-chlorosulfonamides with an active chlorine content exceeding 15%. Consequently, the conversion rate of the starting material to polymeric sodium N-chlorosulfonamide was enhanced from 25–35% to 45–55%. The optimal ratio of reagents per 100 g of starting material was determined to be 10 g of thionyl chloride and 120–150 g of chlorosulfonic acid, with a reaction duration of 4–5 hours. It was confirmed that the type of initial cation exchanger (Na or H form) has no significant effect on the final outcome.