Abstract: Failures of distribution network components caused by different types of extreme disasters pose a serious challenge to the active defense of distribution networks. To address this problem, a disaster risk warning and active defense strategy for distribution networks that takes into account the failure rate of line components is proposed. First, by considering the different characteristics of mobile, distributed, and diffuse extreme disasters, failure probability models for distribution network line components under different typical disasters are constructed. Second, based on the line component failure rate, a unified line risk evaluation index for new distribution networks under extreme disasters is established to quantitatively assess the vulnerable lines in the distribution network. Subsequently, based on the unified pre-disaster evaluation index, the high-risk lines are disconnected, and the existing lines are reinforced in advance. By adjusting the output of distributed power sources and energy storage systems, controlling the opening and closing of contact lines,and transferring power to lost load nodes, while prioritizing the repair of faulty lines from power sources to important loads, an active prevention model is established for the new distribution network under extreme disasters. The established mixed-integer nonlinear programming model is transformed into a second-order conic programming model and then solved using the Cplex+ yalmip optimization solver. Finally, a simulation is conducted based on an urban distribution network, which verifies that the proposed defense strategy can effectively issue warnings for high-risk lines and prevent line failures triggered by disasters through line adjustment. As a result, it ensures that the distribution network can quickly resume normal operation after a disaster, eliminate vulnerable lines, and enhance operational flexibility.