Abstract: Shape memory polymers (SMP) are a kind of intelligent materials that can actively change their shape under external environmental stimuli. Based on the properties of smart materials, they have the advantages of light weight, high strength, and variable stiffness, and show great application potential in many fields, such as aerospace, biomedical, and sensors. This review guides the reader through the latest progress in functional SMP and their composites, 4D printing technology, and applications. The review summarizes functionalized SMP materials based on molecular structure design, functional group grafting, and modification with functional fillers. The formation of hydrogen bonds, the introduction of functional groups, and the construction of network structures play crucial roles in enhancing the performance of SMPs. Simple structures are manufactured by traditional manufacturing technology, and their deformation mode is single, limits the engineering application of intelligent structures. Additive manufacturing technology has the advantages of high precision, high efficiency, high speed, and stable products, and has attracted more and more attention recent years, especially in small batches, personalized, and complex shapes. The emergence of additive manufacturing technology has not only promoted the development of intelligent materials and structures but has also provided new possibilities for their application in new fields. The combination of functional SMP materials with 4D printing technology can achieve rapid processing of complex structures and personalized design, bringing new and smarter development directions the high-tech industries of flexible electronics, intelligent robots, and minimally invasive medicine.