The invention discloses a method for determining a basic power grid framework in extreme conditions. The method comprises the following steps of 1) determining the basic power grid framework, wherein the basic power grid framework is a main power grid framework constituted by power transmission lines of 220kV or above and having significant influence to power grid safety and stability and power supply capability; 2) performing stability level and power supply capability evaluation on the basic power grid framework; and 3) formulating a basic operation pre-arranged plan. By virtue of the technical scheme provided by the embodiment of the invention, the basic power grid framework of the power grid can be screened to ensure basic operation of the power grid in extreme natural disasters or human extreme severe conditions; and by safeguarding the operation bottom line of the power grid, power failure loss caused by disasters can be reduced to the maximum degree.