Abstract: To solve the problem of using opportunity sources for geoacoustic inversion, an inversion method for seabed acoustic parameters based on reconstructing the incoherent beamformed outputs of a horizontal array is proposed in this paper. Unlike the matched-field-inversion, this method makes use of the smooth-averaged principle of the sound field and increases the proportion of the attenuation modes. The simulation results indicate that the proposed method is more sensitive to the attenuation coefficient and tolerant to the error of the source position. The inversion results of experimental data indicate that the attenuation has the nonlinear frequency relationship \left( 0.34 \pm 0.18 \right)f^1.59 \pm 0.27\text dB/m (the unit of frequency is kHz) in the frequency band 30~160 Hz in the experimental sea area. The theoretical transmission loss calculated using the deduced parameters is compared with the experimental data. The results show that the environmental model from the proposed inversion method is more accurate than the matched-field-inversion in characterizing the acoustic field.