Abstract: Diversity-oriented synthesis (DOS) aims to efficiently generate collections of small molecules with diverse appendages, functional groups, stereochemistry and skeletons, thus yielding diverse biological activities capable of modulating a wide variety of biological processes. In this review, we discussed the common strategies employed in DOS with specific examples from recent literature, including reagent-based approach, substrate-based approach, build-couple-pair strategy and privileged substructure-based DOS. The application of some DOS libraries in drug discovery is also presented.