Spintronics, exploiting the spin degree of electrons as the information vector, is an attractive field for implementing the beyond-complementary metal-oxide-semiconductor (CMOS) devices. GaN-based semiconductors, characterized by weak spin-orbit coupling, long spin relaxation time, and Curie temperature higher than room temperature, are considered ideal materials for advancing spintronics. In addition, GaN-based semiconductors possess a variety of heterostructures, and different properties can be combined through energy band engineering, this enables addressing the limitation of GaN-based semiconductors. Nevertheless, there are still challenges in practical applications; for instance, the mechanism of spin relaxation in GaN-based semiconductors is still unclear, and efficient spin gating has not yet been realized. This review examines the progress of spintronics in GaN-based semiconductors, and systematically summarizes the advancements in spin injection, transport, manipulation, and device application. The current challenges and future perspectives on the studies of spintronic devices based on GaN-based semiconductors are also highlighted.