The invention provides an extra-high voltage DC grounding electrode circuit protection system, comprising a tower body, and a lightening conductor cross arm and a grounding electrode wire cross arm on the tower body, lightening conductors respectively fixed on two ends of the lightening conductor cross arm, and grounding electrode wires respectively fixed on two ends of the grounding electrode wire cross arm through an insulator S1 and an insulator S2. The connecting end of the grounding electrode wire and the insulator S1 is connected with one end of a gap C1. The connecting end of the grounding electrode wire and the insulator S2 is connected with one end of a gap C2. The other end of the gap C1 and the other end of the gap C2 are connected with one end of a lightning arrester. The other end of the lightning arrester is connected with the tower body. The technical scheme can reduce accidents of unipolar and even bipolar locking caused by arcing horn flashover of an extra-high voltage DC grounding electrode circuit, and realizes that one lightning arrester can protect two grounding electrode circuits, and ensures correct operation of unbalanced current protective equipment and grounding electrode circuit broken line detection protective equipment, and the system is not influenced by lightning arrester ground capacitance.