Good grounding system is an important guarantee of safe and reliable operation of electric power, telecommunications and electrical equipment. The quality of earth resistance is judged by its size. Finding an accurate, fast, simple and reliable method to measure earth resistance has become urgent in lightning protection and grounding field. This Multifunction Dual-Clamp Earth Resistance Tester can be applied to post and telecommunications, power industry, meteorology, equipment room, power distribution wire, tower transmission line, gas station, factory grounding grid, lightning rod and so on. The instrument not only can adopt the traditional auxiliary ground electrode method to measure the earth resistance, but also can measure the earth resistance without auxiliary ground electrode, which change the traditional measurement principle and method of earth resistance: the use of double jaws non-contact measurement technology, without auxiliary ground electrode and isolating grounding body and load, to achieve the on-line measurement. In the single-point earth system and strong interference conditions, it is recommended that using auxiliary ground electrode to measure the resistance.