It has become a common consensus that the blackout defense framework has been extended to the early warning of natural disasters. Due to the spatial and temporal distribution characteristics of natural disasters’ evolution, and fault uncertainty induced by natural disasters, it is urgent to extend the safety and stability analysis of power system based on deterministic criterion to the operation risk assessment, to extend traditional safety and stability control based on deterministic scenarios listed in three-defense-lines to risk control. In this paper, several key technologies in the field of disaster prevention, namely fault probability assessment and its characteristics, power system security defense predicament and its countermeasures, are reviewed firstly. Secondly, the risk control cost characteristics of power system considering three-defense-lines is analyzed. Finally, risk control strategy is discussed, which is adaptive for probability and loss characteristics in natural disasters. With the proposed strategy, it is easy to set contingency and acquire the preventive control optimization measure that effectively reduces the operation risk of power system. This work is supported by National Key Research and Development Program of China (No. 2017YFB0902600) and Science and Technology Project of State Grid Corporation of China “Research on Power Grid Security Probabilistic Risk Analysis Method and System under Large-scale Forest Fire”.