Abstract: The research is about the effect of a layer of varying density of seabed sediments on spatial correlation of sea-bottom backscattering.The relationship between scattering cross section and spatial correlation is as the incident angle increases,backscattering cross section decreases quickly,the spatial correlation becomes stronger.Therefore,the seafloor density-depth profile is introduced into high-frequency backscattering echo model,which is used to simulate seabottom backscattering and calculate the spatial correlation.The influence of the density gradient on spatial correlation of sea-bottom backscattering is investigated by analyzing the relations between vertical gradient of density and the scattering cross section.As can be seen from the simulation results,the impact of the density gradient on the spatial correlation is found to be more significant.While the density gradient increases,the scattering cross-section broadens and decreases more quickly as the incident angle increases,the radius of the spatial correlation broadens and the spatial correlation becomes stronger.