Selecting the potential fault series properly to optimize the preventive control measures is of important research value to preventing black-out faults. By analyzing typical black-out faults， a method is proposed to select the fault series in power system cascading-fault simulation based on the characteristics of the black-out faults which can be used to help power grid designers and operators spot the lines prone to black-out. In the proposed method， the system load conditions， the weather factors， and the hidden failures of the protective relays are considered in the process of fault-series selection. The application results concerning the IEEE-RTS system have validated the effectiveness of the proposed method.