The utility model relates to a transformer station secondary air switch enclosed-type grounding small ground wire. The small ground wire is mainly used for secondary grounding of devices of a station transformer, a voltage transformer and the like in a transformer station. The small ground wire comprises a pedestal, an spring sheet, a wiring pile, a copper wire, a grounding clamp and an insulation sleeve. A buckle and a slot formed by two blocks are arranged at one side of the pedestal from above down. The wiring pile is fixed at the other side of the pedestal. The spring sheet is fixed on the wiring pile. The insulation sleeve sleeves the spring sheet. One end of the copper wire is fixed on the pedestal through the wiring pile, and the other end of the copper wire is connected with the grounding clamp. A secondary grounding wire can be installed easily in a way that the spring sheet contacts an air switch wiring bolt, and reliable grounding is achieved. The time, labor and money wasting problems and personnel electric shock accidents generated by damage or replacing of the air switch are completely eradicated. The small ground wire has a function preventing incorrect closing of the air switch, achieves grounding dual insurance, and thus on-site safety measures are perfect and reliable.