Abstract: Overhead ground wire (OGW) is an important equipment to prevent transmission wire from being struck by lightning. When OGW is struck by lightning, the sliding motion of arc root causes different damage mechanism. Therefore, it is necessary to analyze the sliding motion of arc root first, so as to provide data support of sliding displacement for the research of damage mechanism. In this paper, the sliding motion model of arc root along OGW is established based on the arc chain modeling method. By analyzing the main influence range of the electromagnetic force, the space boundary of modeling is narrowed, so the calculation amount is greatly reduced. Then, the model is verified by the needle-wire discharge experiment in the laboratory. Finally, based on the established model, the factors affecting the sliding displacement of arc root are analyzed, including thermal buoyancy, return stroke and continuous current. The results show that the effect of thermal buoyancy can be ignored under the action of return stroke. The sliding displacement of arc root is positively correlated with the wavelength time, but not with the wave head time. However, under the action of continuous current, thermal buoyancy affects the evaluation result of arc root sliding displacement, and the maximum error is more than 25%.