The invention discloses a method for measuring impact grounding impedance on a site based on large impact current. The method comprises the following steps: wiring a current electrode, wiring an impact current generator, wiring an injection point voltage signal measuring wire, and wiring an injection point current signal measuring wire. By the method provided by the invention, a dispersing property of the impact current in soil can be really reflected, actual measurement on an impact grounding property of impedance under the large impact current can be achieved, the impact grounding impedance can be accurately measured, an impact property of a grounding body can be easily mastered, design, construction and running of lightning protection engineering can be instructed and inspected, the integral safety and the integral reliability of the engineering are improved, and the operability is good.