The invention relates to a corrosion prevention technology for grounding net metal materials, in particular to a method and a device for protecting a power facility grounding net. Focused on an electrochemical corrosion principle, the invention meets the requirement on grounding net protection in different soil environments by reducing the potential of a grounding body for inhibiting grounding net corrosion and by selecting different materials, technologies and methods, including surface treatment of grounding net materials, the material, the weight, the quantity, cladding materials of sacrificial anodes, and connecting and installation mode. By reducing the potential of the grounding body for inhibiting grounding net corrosion, a grounding net is protected and the problems of short service life and large resistance of the grounding net and high equipment replacement cost can be solved. The corrosion prevention technology is simple and practicable, reduces the grounded resistance of the grounding net to below 0.3 ohm averagely after being implemented, needs low investment, can prolong the service life of the grounding net and can achieve very remarkable economic benefits.