Foreign matter is one of the main causes of breakdown fault in GIS equipment. Under the operating voltage, the foreign matter in GIS equipment moves randomly under the action of electric field force, so it is difficult to determine the characteristics of the internal foreign matter in field detection. In this paper, the mechanical characteristics of foreign bodies in GIS equipment are analyzed, and the 126 kV GIS equivalent model is established, and the dynamic track of foreign bodies in GIS under the action of AC voltage and pulse voltage is compared. The results show that the jumping track of foreign matter particles in GIS equipment is irregular under AC voltage. When a specific pulse voltage is applied, the jumping rule of foreign matter particles in GIS is controllable, and its jumping height and time interval are basically the same.