The invention provides a method for searching for dangerous power transmission sections. The method includes the following steps that a digraph is formed according to the operating state of a power grid, and weights of all the sides of the digraph are counted; whether the sections in the digraph are effective sections or not is judged; the number n of the effective sections is counted, and if n is smaller than a specified threshold value N, section sensitivity analysis is conducted, and information of the dangerous power transmission sections, transmitting ends or receiving ends is output; otherwise, the sides with the smallest weights are combined. The method automatically searches a system for the dangerous power transmission sections and the functions for generating information of the transmitting ends or the receiving ends are achieved according to the actual operating state of the power grid. The method is rapid and effective, no information needs to be preset, and the method excellently adapts to different operating states of the power grid and can be used as the manually-set function supplement of the power transmission sections or as a tool for analyzing the stability characteristic of the power grid.