Abstract: The VSC-UHVDC system contains a large number of energy storage components, which is prone to serious continuous overvoltage when the inverter station is locked due to a ground fault. In order to avoid serious reverse current overvoltage hazards to the safety of equipment and system, the fault characteristics of the long distance VSC-UHVDC system under typical fault conditions such as faults on the valve side of transformer and ±400 kV busbar are analyzed, the mechanism of continuous overvoltage is studied, the influences of the continuous voltage are evaluated, and some measures to suppress overvoltage are proposed. The research indicates that the optimal configuration scheme of arrester can effectively reduce the continuous voltage, which can reduce the overvoltage of the upper bridge arm of high voltage converter by 38% and the overvoltage between the terminals of high voltage converter valve by 29%. The auxiliary control strategy can effectively reduce the stress of high energy arrester by more than 30%. The transient simulation model on the PSCAD/EMTDC is built to verify the correctness of overvoltage mechanism and the effectiveness of overvoltage suppression measures. The results can provide theoretical supports for the construction of the first batch of VSC-UHVDC projects in China, and are beneficial to ensuring the safety of DC system operation.