Abstract: To reveal the dispersion and attenuation characteristics of ground-penetrating radar (GPR) electromagnetic waves in karst media, the frequency-domain complex permittivity of typical karst media in Guangxi is measured by a vector network analyzer. The dispersion parameters are obtained by fitting a second-order Debye model. Numerical simulations of the dispersion and attenuation properties of GPR waves are conducted based on the finite-difference time-domain (FDTD) method, and the reliability of the numerical approach is verified by physical model tests. The results indicate that the frequency-domain complex permittivity of karst media is closely related to rock type, clay-filling parent rock, water content, and the mineralization degree of karst water. Both the real and imaginary parts of the complex permittivity increase with higher water content, while the mineralization degree significantly affects only the imaginary part. The attenuation rate of electromagnetic waves in different soluble rocks follows the order: marl > limestone > dolomite. The attenuation rate of wave amplitude in clay fillings increases with higher water content and mineralization degree. Over short propagation distances, the peak frequency of electromagnetic waves is less affected by water content but more influenced by mineralization. The attenuation coefficient and quality factor derived from the frequency-domain complex permittivity effectively explain the attenuation mechanisms of wave amplitude and peak frequency in soluble rocks and clay fillings. A case study from practical engineering demonstrates that the dispersion and attenuation parameters of GPR signals in karst media, obtained through measured complex permittivity and second-order Debye model-based numerical simulations, can serve as a reliable basis for identifying unfavorable karst geological bodies.