As one of simplest chemical reagents, iodine has promoted diverse organic transformations, which have attracted much attention in recent years. The present review summarizes three basic chemical features of iodine in organic synthesis: the oxidative reactivity, the acidic reactivity and the electrophilic reactivity, along with the introduction of corresponding representative examples. Furthermore, the iodine-catalyzed reactions involed in the synthesis of heterocycles, organic coupling reactions, the C-H functionalization, and other applications are also presented in this review.