During ground operation and low altitude flight of an aircraft, ground vortex phenomena or inhalation of foreign matter can occur in the engine inlet tract, causing distortion of the internal flow field. This poses a potential hazard to engine integrity and performance stability. However, the characteristics of ground vortices are complex and different under different flight conditions. In this paper, an experimental method is used to systematically investigate the variation rule of the ground vortex nucleus height with the off-ground height and the aerodynamic interface (AIP) Mach number. The scale model of NACA-1-85-100 inlet was utilized for the experiment, and the ground vortex structure was captured by particle image method. The findings indicate that as the AIP Mach number rises, the altitude of the ground vortex core diminishes, while it increases with greater distance from the surface. At the same time, the ground vortex under different conditions will bring different degrees of influence on the total recovery coefficient of the inlet AIP. These findings provide valuable physical insights into how ground vortex characteristics are affected by the flight environment and engine operating conditions. The research in this paper will help optimize inlet design to minimize adverse effects on aero-engines during critical flight phases close to the ground. Overall, this study improves the understanding of transient inlet flows affected by near-ground effects.