Abstract: In the fully mechanized caving mining of extra-thick coal seams, grasping the variation law of top coal thickness with intercalated gangue in advance is crucial for accurate and efficient coal drawing at the working face. Although ultra-wideband ground-penetrating radar technology serves as a new method for top coal thickness detection, insufficient understanding exists regarding the electromagnetic wave field characteristics of complex top coal structures with intercalated gangue, and the ability to accurately identify the position, thickness and properties of intercalated gangue needs improvement. Based on the Finite-Difference Time-Domain principle, a ground-penetrating radar electromagnetic wave attenuation model is established, the propagation attenuation mechanism of electromagnetic waves in coal-gangue mixed media is derived, and the correlation between medium parameters and attenuation laws is clarified. Numerical simulation analysis is performed using GprMax software, geological models combining different intercalated gangue positions, thicknesses and properties are constructed, and the propagation characteristics of electromagnetic waves are systematically explored. Eight indoor test models with different coal-gangue structures are built, and on-site measurements are conducted at the 12240 fully mechanized caving face of an extra-thick coal seam with intercalated gangue in a coal mine of the Western Henan Coalfield to verify the reliability and engineering applicability of the research results. The results show that: The propagation speed of electromagnetic waves in coal seam media is not affected by electrical conductivity, decreasing monotonically with the increase of coal seam relative permittivity and slightly with the increase of center frequency. However, the peak electric field intensity at the coal-rock interface decays continuously with the increase of coal seam electrical conductivity, showing a significant negative correlation with relative permittivity and a weak positive correlation with center frequency. Electromagnetic waves are reflected at the upper and lower interfaces of intercalated gangue, with propagation speed and electric field intensity in intercalated gangue significantly lower than those in coal seams, and the attenuation amplitude changing synchronously with medium properties. Changes in intercalated gangue position induce wavelength-related constructive or destructive interference. Propagation speed decreases linearly with the increase of intercalated gangue thickness, and the attenuation amplitude of peak electric field intensity at the coal-rock interface tends to stabilize when the thickness exceeds the vertical resolution threshold. The increase of intercalated gangue relative permittivity leads to a significant decrease in wave speed and field intensity attenuation. Based on the obtained wave field response characteristics, an optimal center frequency model of radar electromagnetic waves considering both penetration depth and resolution is constructed, with calculation errors controlled within 7%. A precise hierarchical identification method for intercalated gangue structures is proposed: by extracting the two-way travel time of reflected waves at the upper and lower interfaces of intercalated gangue and combining with known coal seam electrical parameters, the position, thickness and relative permittivity of intercalated gangue are inverted to achieve synchronous interpretation of multiple parameters of intercalated gangue. Verification results from indoor tests and underground measurements show that the inversion error of this identification method fluctuates around 5%, indicating high accuracy. The revealed propagation wave field response characteristics of electromagnetic waves in complex coal-gangue media and the variation law of interface reflected waves with structural changes provide a theoretical basis for the engineering application of ground-penetrating radar in underground coal mines.