Abstract: The present disclosure provides a method for preparing multi-component polymers through post-polymerization modification, used to functionalize polysulfonyl imidate polymer including a dispersing polymer reactant, an electrophilic substitution reagent and a catalyst in an organic dispersant; adding acid-binding agent to react at room temperature for 4-48 h; obtaining the precipitate when the reaction finished; washing and drying the obtained precipitate to get the functionalized multi-component polymers. The present disclosure involves a low polymerization temperature, allowing for the reaction to occur at room temperature. Additionally, the conversion rate is high, and the applicable electrophilic substitution monomer reagents have a wide selection. Besides that, the synthesis cost of the reaction is low due to the widespread availability of common chemical reagents such as catalysts, organic dispersants, acid binding agents, and other reaction reagents.