Abstract: To reduce the traditional grounding grids inspection workload and the subjective errors, we propose a novel method based on the electromagnetic induction theory, through which we can monitor the corrosion condition of ground grids. We design a networking grounding grids corrosion detecting system, which consists of small size wireless electromagnetic signal sensing nodes (wi-SN). By laying wi-SN in the selected location and injecting the specific frequency current to the grounding grid, we can automatically measure the electromagnetic signal. The sequential probability ratio test based algorithm is, thus, used to estimate the corrosion status of the earth grounding material. Experimental results obtained with the so-developed prototype system showed that the system could give early warning of corrosion condition.