Abstract: Copper sulfide (CuS)， a p-type semiconductor material， exhibits considerable potential as an electromagnetic wave absorber owing to its tunable dielectric response and abundant sulfur vacancies. However, its intrinsic microwave absorption ability remains weak because of a single loss mechanism and poor impedance matching. Herein, we propose a heterointerface engineering strategy to unlock the full absorption potential of CuS. Leveraging the metallic nature of MXene and the semiconductor characteristics of CuS, we constructed abundant metal-semiconductor heterointerfaces in MXene/CuS composites via a one-step hydrothermal method. During this process, partial oxidation of MXene leads to the formation of TiO₂ on its surface, enabling regulation of the MXene-TiO₂-CuS heterointerface composition. As a result, the optimized MCu5 delivers a 7.14 GHz effective bandwidth at a thickness of 2.6 mm, attributed to the multi-phase heterostructure and synergistic loss mechanisms. This study establishes a clear correlation between interfacial engineering, dielectric response, and absorption behavior, providing new insights and experimental guidance for the design of high-performance metal-semiconductor composite microwave absorbers through interface engineering.