In order to obtain the mesh conductor place and mesh structure of grounding grid without drawings, a detecting method is developed. A sinusoidal wave current of specified frequency is injected directly into grounding grid by two ground lead wires. At the same time, the distribution characteristics of the surface magnetic induction intensities are measured, and then the conductor places and mesh structure could be detected by the distribution laws. The simulation calculation is shown that the method is feasible. A special current power and moving system for measuring faint magnetic induction intensities and fitting software system are designed. Experements and applications prove that the method is accurate and the system is reliability. It can be used in the engineering practice.