The multi-energy composite field micro-electrodeposition processing technology is used to prepare colorful structural coloration magnetic Al₂O₃-Co composite films each with a gradual microstructure. Under the action of the deposition electric field and the deflection electric field perpendicular to it, the microstructure, optical properties and magnetic properties of the composite films show gradual characteristics along the direction of the deflection electric field. By establishing an equivalent model of the microstructure, the mechanism of the microstructure change of the composite film is theoretically analyzed. Through software simulation, the distribution of Co ion deposition current density along the direction of the deflection electric field is quantitatively analyzed. The simulation results are consistent with the theoretical and experimental results. Through this study, we find that the micro-electrodeposition processing technology with using multi-energy field composite can control the micro-domain structure of the composite film from a microscopic point of view, and achieve the fine control of the magnetic and optical properties of the film micro-domain.