Fracture-related deterioration is common in grottoe temple rock masses, with water seepage exacerbating the issue, complicating cultural relic preservation. This study explores the dynamic response mechanism of radar wave propagation to fracture seepage in sandstone. Firstly, a transient model, based on physical parameters and Richards equation, is established. Then, the finite difference time domain method is used to numerically simulate the fractured seepage in sandstone with ground-penetrating radar(GPR). Finally, Hilbert transform is used to extract the instantaneous attributes and analyze the radar wave field responses under different seepage durations. Simulation of sandstone fracture seepage reveals that fracture seepage increases the dielectric constant of seepage area, enhances radar wave scattering in this area, and causes the instantaneous amplitude of the radar wave scattering to increase with the increase of water saturation. The reselts provide an important theoretical support for GPR in detecting micro-seepage fractures in sandstone.