This paper reviews recent advances in polymer-supported acid catalysts and their applications in organic synthesis. The discussion is mainly divided into the polymer-supported Bronsted acids and Lewis acids and subdivided by the nature of the reactions. In the former section, organic reactions catalyzed by polymer Bronsted acids, such as polymers functionalized with sulfonic acid (e.g., Friedel- Craft reactions, etherification, esterification, aldol reaction, multicomponent reaction, isomerization/oligomerization of alkenes, hydration of alkene/dehydration of alcohols, protection/deprotection of alcohols, etc) are discussed. Specific emphasis is placed on esterification for biodiesel production. In the latter section, organic reactions catalyzed by polymer Lewis acid (e.g., Diels-Alder reaction, aldol reaction, Michael reaction, addition reaction to carbonyl group, etc) are discussed. Because of convenient access to diverse ranges of polymer support structures and importance of acid-catalyzed organic reactions in organic synthesis, these polymer-supported acid-catalyzed reactions will continue to play critical roles in environmentally friendly organic synthesis and combinatorial library development.