Abstract: Compared to high-frequency superconducting niobium cavities, superconducting high-frequency niobium coating cavities have a series of advantages such as insensitivity to DC magnetic field, high thermal stability, low cost, and the copper cavity niobium coating process is the basis for the preparation of Nb₃Sn and NbN, as well as superconducting-insulating-superconducting (SIS) composite films on the surface of copper cavities. Therefore, a DC magnetron sputtering method was used to deposit niobium films on the inner wall of the high-frequency cavity of the copper in order to explore the copper cavity niobium coating process. The internal defects, surface morphology, and crystalline structure of the niobium film were characterized by means of FIB, SEM, and XRD. The results show that by controlling the dusting free of the coating vacuum chamber, reducing the coating time and discharge air pressure, and controlling the movement of the magnetic ring, a niobium film with uniform axial distribution in the copper cavity, a Tc value of 9.26 K, and good surface continuity was obtained. The results of the vertical test of the copper-plated niobium cavity showed that the cavity performance reached 5 MV/m at Q₀>10⁸, corresponding to the peak magnetic field is 24 mT, achieving superconductivity in the coated cavity. This provides a good basis for further improving the quality of the niobium film, improving the performance of the coated superconducting cavity, and attempting to coat other superconducting materials (NbN, Nb₃Sn) on copper substrates.