Abstract: An isobutylene-based cationic salt ionic polymer, a preparation method therefor, and the use thereof are provided. The polymer has a structure represented by formula (2) and/or formula (3), and optionally, a structural unit A represented by formula (1), a structural unit B represented by formula (4) and a structural unit C represented by formula (5), Q being formula (6), formula (7), formula (8) or formula (9). The side group and the main chain of the polymer both contain cationic salt groups, so that the polymer has a high polyionic degree and thus can be used as an antibacterial agent for preparing antibacterial polymer materials, such as antibacterial plastics, antibacterial rubber, antibacterial fibers and antibacterial coatings.