The invention discloses a power grid power transmission section determination method based on distribution factors, which comprises the following steps: determining on-off distribution factors corresponding to lines in a to-be-analyzed power grid one by one according to a power flow analysis result for the to-be-analyzed power grid; determining a plurality of to-be-selected power transmission sections according to the on-off distribution factors corresponding to the lines, the absolute value of the on-off distribution factor between every two lines in each to-be-selected power transmission section being greater than a pre-specified first threshold H1; screening the to-be-selected power transmission sections one by one, and when lines with a series connection relationship exist in the to-be-selected power transmission sections, removing the lines with the series connection relationship from the to-be-selected power transmission sections, wherein all to-be-selected power transmission sections obtained after the series connection relation line is removed are determined as the power transmission sections of the to-be-analyzed power grid. The method can quickly and accurately search thepower transmission section in the interconnected large power grid.