As a unique reflux path for trains, the 'train-rail' mobile grounding system has the double functions - the traction power feedback and the transmission of train's communication signal. With the constant increment of operational velocity and traction power for high-speed railway, the coupling relationship existing in the 'train-rail' mobile coupling grounding system becomes complicated, when the train's wheels roll over the insulated joint. It may result in the frequent occurrence of rolling arc and the ablation of rail ends and insulated joints, which might lead to the series connection of the rail circuit or even trigger the misjudgment of operational control system. As the impedances existing in the grounding system vary transiently when the relative distance between the train and the fixed terrestrial grounding installations changes, the dynamic coupling mechanism between the transiently-varying topology of reflux path and the distribution of reflux at each grounding wheel tends to be analyzed. Depending on the built 'catenary-train-rail' dynamic coupling grounding reflux model, the correlation between the 'train-rail' mobile grounding reflux and the evolutionary process of rolling arc is explored. In order to reduce the risk of 'wheel-rail' arcing phenomenon, a novel method of automatically controlling insulated joint is proposed herein, as its feasibility is verified via the comparison with the original type of the insulated joint.