Disclosed is a composite functional resin, having the basic structure of Formula (I) and/or Formula (II), wherein AX is a quaternary ammonium group. In view of the problems that the existing resins have poor anti-interference ability, and poor ability to remove dissolved organic matter, disinfection by-product precursors, and anions such as nitrate, sulfate, phosphate and arsenate in water while sterilizing, the composite functional resin of the present invention has the ability to efficiently remove dissolved organic matter, disinfection by-product precursors, and anions such as nitrate, sulfate, phosphate, and arsenate in water, and has the advantages of efficient sterilization and high anti-interference ability. The composite functional resin can be applied in sterilization and water treatment.