Abstract: In order to enhance the fatigue resistance of copper-based flexible thin films, copper-coated carbon nanotubes (CNTs) were incorporated into the ink formulation to prepare copper-based composite films, with a focus on analyzing the influence of copper-coated CNT content on the microstructure and fatigue resistance of the composite films. The impact of copper-coated CNT content on the microstructure and fatigue resistance of the composite films was emphasized and examined. The results indicated that when the copper-coated CNT content was 1wt.%, a highly conductive and fatigue-resistant copper-based composite film was obtained, with a resistivity of 17.73 μΩ·cm and a resistivity change rate of 49%. This was attributed to the copper-coated CNTs being connected within the interstices of the copper structure, thereby serving as additional conductive pathways that improved conductivity. Furthermore, at grain boundaries, they impeded dislocation motion, thus retarding the extension of cracks and inhibiting the formation of sintering necks, consequently enhancing the fatigue resistance of the composite film. Due to the minimal interface disparity between the copper-coated layer of CNTs and the copper matrix, during sintering, diffusion occurred towards the matrix surface, reducing the surface area of the matrix compared to the volume of copper particles. When the copper-coated CNT content increased to 2wt.%, the volume and quantity of copper particles increased, leading to a decrease in the continuity of the structure. Consequently, this resulted in a reduction in both the conductivity and fatigue resistance of the composite film. Therefore, an appropriate amount of copper-coated CNTs could enhance the conductivity and fatigue resistance of the composite film.