Abstract: To study the influence of the brush support stiffness on the dynamic characteristics of the multi-channel brush-slip ring contact pair, the brush is simplified as a Euler–Bernoulli cantilever beam, and the theoretical formula for calculating the brush support stiffness is derived. Moreover, a finite element model for the rotor system of the high-speed electrical feedthroughs with slip-ring glued slender shaft is established, and the support stiffness of the multi-channel brush is considered to study its effects on the rotor. This paper presents a numerical simulation analysis for the finite element model of the rotor system. Based on simulation, the system vibration mode diagram, Campbell diagram and critical speed deviation margin are obtained. Research results show that the brush support stiffness can be a significant factor in the first-order bending mode of the slender shaft structure of the rotor.