Taking the near-ground short-slot air intake of shrinkage ratio as the research object, the influence of velocity gradient on the structure and aerodynamic characteristics of the ground eddy current field under the condition of upwind flow is obtained by numerical simulation. Studies have shown that velocity gradients are the main factor affecting ground vortices. The ground vortex structure is significantly different under different velocity gradients. The ground vortex formed by the near-surface section under the velocity gradient in the Y direction is a pair of vortices with opposite directions of rotation. The larger the velocity gradient, the greater the ground vortex intensity and the total pressure distortion index. And the peak will appear hysteresis. In the Z-direction velocity gradient, the ground vortex formed by the near-surface section is a single vortex structure, and a vortex body is formed above the inlet passage. The ground vortex intensity and total pressure distortion index will increase first and then decrease, and the peak will not appear hysteresis.