The invention provides an automatic device for crossing a high-voltage transmission line lightning conductor quakeproof hammer and a crossing method of the automatic device. The automatic device comprises a main frame, two L-type rocker arms installed on the main frame, a driving mechanism driving the two L-type rocker arms to swing, and a control system controlling the driving mechanism to act. One end and the bent position of each L-type rocker arm are provided with a supporting wheel and a walking wheel through pin shafts respectively. When the automatic device moves on an overhead ground line, after the control system automatically detects that the quakeproof hammer exists, the automatic device can automatically cross an obstacle in front of the automatic device through control over lifting up and placing down of the supporting wheels, and tools and small devices are rapidly conveyed to the designated position to be maintained; when the automatic device collides with the quakeproof hammer, the tools and insulation ropes do not need to be repeatedly taken down, the risk of manual operation is reduced, a worker does not need to make contact with the overhead ground line, hot-line working can be achieved, and safety and efficiency of the maintenance work of the electric transmission line are improved.