Multi-material components featuring high performance and design flexibility have attracted considerable attention, providing solutions to meet the performance demands of high-end equipment components. Achieving material diversity in additive manufacturing (AM) is a fundamental step towards manufacturing multi-material components. Wire arc additive manufacturing (WAAM), an important branch of AM technology, boasts notable advantages in the efficient and customized preparation of large-scale parts due to its high deposition efficiency and unrestricted forming size. However, achieving material diversity in WAAM, constrained by its reliance on wire-form raw materials, has emerged as a compelling challenge. Wire innovation, including multiple, stranded, and cored wires, have furnished solutions to this challenge. To this end, this review provides an overview of the current developments in WAAM via wire innovation and suggests future research directions, aiming to serve as a reference for th