As to the power supply main loop in the medium-low speed maglev system which employ the third trail, a mathematical model of resistance capacitance (R-C) ground network was built, and ground current characteristics were analyzed from its bode diagram and measured spectral data. The theoretical and experimental results showed that the accumulation and discharge of vehicle body potential had dynamic balance characteristic, by further optimizing the R-C parameters as well as separating the suspension modulars from the vehicle body, a rapid current diversion channel was formed to improve the system grounding performance.