Abstract: The paper proposes a method of geoacoustic parameter inversion of the horizontal layered seabed based on the spatial variation characteristics of vertical wave impedance for the geoacoustic parameter inversion problem of the deep sea. First, the expression of wave impedance under the normal mode theory is derived, and the spatial fluctuation characteristics of wave impedance are analyzed. Then, based on the fact that vertical wave impedance carries richer acoustic field information, a target function related to vertical wave impedance is established for geoacoustic parameter inversion. Finally, a posterior probability distribution is given to analyze the reliability of the inversion results. The simulation calculation and processing results of experimental data show that the peak values of the probability density distribution of the thickness, density, sound speed, and attenuation of the sediment layer, as well as the density, sound speed, and attenuation of the substrate, are relatively sharp, which proves that the proposed method can effectively invert the geoacoustic parameters of the seabed in deep-sea environments. The comparison between the transmission loss calculated by substituting the inversion results into the model and the transmission loss of the received signal is consistent, and the average errors of range and depth inversion of the sound source by using the inverted geoacoustic parameters are 10.83% and 10.65% respectively.