Abstract: In order to improve the inversion efficiency and reduce the coupling of the geoacoustic parameters, a linear inversion method of the geoacoustic parameters of sediment layer with low sound speed is proposed. Based on the reflection coefficient of the plane wave of the two-layer seafloor from the quasi-linear sound speed profile, the relationship between the different reflection characteristics and the relevant geoacoustic parameters is analyzed, including the angle of intromission and the maximum reflection loss at the angle of intromission, interference fringe, and the corresponding cost function is constructed. Combined with sensitivity analysis and stepwise inversion strategy, geoacoustic parameters of sedimentary layer with low sound speed are inversed step by step. This method is applicable to the case that the sound speed gradient of the low sound speed sediment layer is constant. The method is verified by part of the measured seabed reflection loss data from the new England mud patch. The inversion results are basically consistent with the relevant trans-dimensional inversion results, the inversion error is 0.1% for the sound velocity ratio, 0.3% for the density ratio, 14.6% for the absorption coefficient, and 15.8% for the sound speed gradient. The proposed method not only effectively weakens the coupling between some geoacoustic parameters, but also gives the best estimate of the power term that determines the shape of the quasi-linear sound speed profile.