The invention discloses a portable grounding wire comprising a first clamp plate. A first connecting piece is connected on one side of the first clamp plate, and the inner side of the first connectingpiece is provided with a limiting groove. A spring is installed on one side of the first clamp plate, and a second clamp plate is connected on the other end of the spring. A second connecting piece is installed on one side of the second clamp plate close to the spring, and a limiting block is connected on the other side of the second connecting piece. The limiting block and the limiting groove are slidably connected. A grounding cable is connected on the other side of the second clamp plate. An extension plate is installed on the bottom end of the first clamp plate. According to the portablegrounding wire, the extension plate having the thickness with that of the first clamp plate is utilized to reduce the time for comparing the edge height of the extension plate with that of the first clamp plate so that the purpose of accelerating the connection work between the extension plate and the first clamp plate is conveniently realized, and the extension plate can play a guiding function to the device.