Abstract: As a kind of electronic device for continuous transmission of electric energy and signal, the large slip-ring requires a surface modification with high wear resistance and good electrical contact performance during long-term rotation. Palladium-nickel plating (80/20) is an ideal choice. The preparation process of surface palladium-nickel plating (80/20) on the large slip-ring is discussed in this paper. Both effects of plating solution composition and current density on the thickness and content of palladium-nickel plating and effects of the plating thickness on plating solution composition are studied. The deposition rules of palladium-nickel plating on different ring structures and internal & external surfaces are also explored. The palladium-nickel plating with a thickness of 2 滋m to 2 0 滋m and a palladium content of 77.6 % to 83 % can be obtained through selection and improvement of the preparation process. Finally, the dynamic running condition of the large slip-ring modified by the palladium-nickel plating is tested. The terminal resistance of slip-ring is 30 m赘to 34 m赘and the resistance fluctuation is less than 10 m赘during 700 000 dynamic running times. The test results agree with the technical specifications of dynamic running.