The differences in dominant polarization mechanisms of water-bearing porous media across various frequency bands lead to dispersion in the dielectric permittivity. The broadband dielectric spectrum contains critical information about the multiscale structural characteristics and component contents of the porous medium. Time-domain reflectometry (TDR) is suitable for MHz to GHz frequencies, while the electrode-based method is applicable to frequencies below MHz. However, due to structural differences between TDR probes and electrodes, their testing targets are inconsistent, making it impossible to jointly interpret test data. To address the requirement for broadband electrical parameter testing of hydrate-bearing marine sediments, a novel testing scheme combining segmented-coating TDR and two-electrode methods was proposed. A new embedded- and segmented-coating TDR probe was designed, and a finite element numerical model was established. Orthogonal experiments were conducted and the optimal parameters were obtained, i.e., 3 gaps with the lengths of 2mm and the coating with the thickness of 0.5mm. A finite element numerical model for the two-electrode method was developed, and numerical simulations were conducted to determine the probe's geometric factor for converting impedance into complex conductivity. Correction models for measured values influenced by embedded- and segmented-coating were established for conductivity and dielectric permittivity measurements. Simulation tests based on the joint TDR and two-electrode methods were performed on porous media under different hydrate saturations using the same probe to achieve broadband (mHz-GHz) electrical parameter testing. Simulation results show that both the high-frequency dielectric permittivity and conductivity measured by the TDR method decrease with increasing hydrate saturation, with the average relative errors of 2.44% and 6.22%, respectively. The low-frequency equivalent dielectric permittivity measured by the two-electrode method also decrease with increasing hydrate saturation, with the average relative error of 2.20% in the frequency band dominated by electrical-double-layer polarization. This research provides a theoretical and technical support for the future development of experimental apparatus for measuring broadband electrical parameters of hydrate-bearing marine sediments.