Ground down lead and earth mat of electrical equipment reliable and effective connection is the fundamental guarantee of instrument safety operation. Ground down lead is the connection part of electrical equipment and earth mat. In the long-term running, the connection part may be rusty even ruptured due to moisture and other factors, which will cause the resistance increases which at connection point of ground down lead and the main earth mat, and thus cannot meet the requirements of electrical power regulations and standard. This device is specially used to test the electrical integrity of earthing device