Abstract: A method for detecting a topological structure of a grounding grid under extremely cold condition, includes the following steps: in a substation in an extremely cold area, determining a measuring area S on a ground surface of a grounding grid according to the positions of branches and nodes of the grounding grid in a selected area, acquiring dynamic current values of the branches and nodes through a current sensor based on TMR tunnel magnetoresistance, and then indirectly acquiring the magnetic induction intensity of the measuring area S through conversion; calculating moduli of first to third derivatives of magnetic induction intensities; and determining specific positions and laying depths of the branches of the grounding grid according to peak distances between main lobe peaks and side peaks between strong peaks of the moduli. According to the method, the calculation amount is greatly reduced, and the detection method has strong anti-interference.