The rapid development of additive manufacturing technology has offered a new avenue for designing and fabricating high wave-absorbing meta structures. In this study, the mechanical properties and broadband absorption performance of Poly-Ether-Ether-Ketone (PEEK)–based electromagnetic wave–absorbing composite materials was investigated. The high-performance polymer PEEK was used as the matrix, and the materials with electromagnetic wave loss, such as reduced graphene oxide, Carbonyl Iron (CI), and Flake CI (FCI), were used as absorbers. Based on the theory of impedance matching, a wave-absorbing structure with a gradual impedance gradient was designed and printed. The test results showed that at the 2.0–18.0 GHz frequency band, the coverage rate of the effective absorption bandwidth was up to 72.0%, the average optimal reflectivity was –18.09 dB, and the wide-angle absorption range was 0°–30°. The advantages of additive manufacturing technology in designing and fabricating wave-absorbing structures are presented, demonstrating that the technology is an effective method for creating broadband absorbing structures.