This chapter focuses on the research progress of deployable composite structures in aerospace applications. Driven by the rapid development of aerospace technology, there is an urgent demand for high-performance space deployable structures. Elastic strain energy-driven large-deformation flexible composite structures have become a research frontier due to their advantages such as high packing efficiency and light weight. The chapter systematically reviews deployable composite hinges (including tape springs, integral hinges, and combined hinges), booms (tubular, non-circular, and bistable types), reflectors (taco-shaped, petal-shaped, umbrella-shaped, and warp-rid types), and composite helical structures, covering design, modeling, fabrication, optimization, and applications. It also outlines the book’s structure, which systematically introduces theoretical models, computational methods, numerical simulations, optimization designs, and engineering applications of large-deformation flexible composite structures.