In this study, manganese-cobalt-nickel-oxide (Mn-Co-Ni-O, MCNO) thin films were prepared on silicon substrates by radio frequency (RF) magnetron sputtering and post-annealing. The crystal structure and surface morphology of the thin films were characterized by X-ray diffraction and scanning electron microscopy, and their optical properties were tested and analyzed by optical testing instruments. The effect of RF sputtering power (60~100 W) on the surface morphology, crystal structure and optical properties of MCNO thin films were analyzed. The surfaces of the films obtained under 60~90 W were dense and uniform, but the surface grain size of the MCNO thin films obtained under 100 W increases significantly. The phase analysis shows that the MCNO thin films deposited by RF magnetron sputtering are mainly spinel structures, and the sputtering power has a significant effect on the crystal quality and preferred orientation of thin films. The crystal quality of the MCNO thin films obtained under 80 W is the best. At the same time, the Raman spectroscopy test also shows that the MCNO thin film exhibits the strongest Mn4+-O symmetrical bending vibration and the smallest compressive stress. Ultraviolet-visible-near-infrared spectroscopy analysis show that the absorption range of MCNO thin films is mainly in the visible-near-infrared band, and the MCNO thin films obtained under the sputtering power of 80~90 W show stronger absorption peaks in the near-infrared band. The change of the RF sputtering power can affect the thickness and crystalline quality of the thin film, thereby regulating the optical band gap of the thin film. The luminescence of the defect peaks at different sputtering powers was measured by photoluminescence spectroscopy, and the thin films deposited at 80 W have the strongest UV emission peaks, demonstrating that varying the sputtering power can effectively improve the defects and crystal quality.