The invention relates to a system for preventing DC power supply bus voltage failure and an operation method thereof. The system for preventing DC power supply bus voltage failure runs in a DC power supply system including a battery pack and the battery pack having m serially connected cells, and includes at least one intelligent detection module and one or more DC/DC modules, the intelligent detection module includes a bus voltage acquisition circuit unit, a control output circuit unit and an intelligent determination circuit unit, wherein the bus voltage circuit unit is connected with a DC power supply bus, and the DC/DC modules have input and output interfaces. The system can monitor and compensate for possible DC bus voltage failure, and ensures the safe and stable operation of the DC system.