The invention discloses a three-dimensional digitalized monitoring device and method for a substation grounding grid. The three-dimensional digitalized monitoring device comprises a data acquisition system, a grounding grid state evaluation system, a three-dimensional imaging system, a digital information storage system, a state information output system and a fault alarm system, wherein the signal output end of the data acquisition system is connected with the signal acquisition end of the grounding grid state evaluation system; the first signal output end of the grounding grid state evaluation system is connected with the three-dimensional imaging system; the second signal output end of the grounding grid state evaluation system is connected with the digital information storage system; the third signal output end of the grounding grid state evaluation system performs displaying through the state information output system; the signal output end of the state information output system is connected with the signal input end of the fault alarm system. By utilizing the three-dimensional digitalized monitoring device and method, the impedance of the grounding grid can be subjected to three-dimensional imaging and diagnosis, and a digitalized detection archive further can be created for each detected grounding grid, so that a state of the grounding grid can be tracked for a long term.