Abstract: The fundamental principle of the spatial correlation characteristics of sea-bottom backscattering is expounded. The Kirchhoff model is introduced to simulate sea-bottom backscattering and the spatial correlation is calculated. Some sediment characteristic parameters, such as the ratio of sediment mass density to water mass density, the ratio of sediment sound speed to water sound speed, the attenuation coefficient of sound waves, the strength and exponent of sea-bottom interface roughness spectrum, are considered while simulating and their influences on spatial correlation are analyzed. By establishing the expressions of the sediment characteristic parameters with the logarithmic sediment grain size, the changing tendency of the spatial correlation is obtained. The width of the major lobe of the spatial correlation narrows while the logarithmic sediment grain size increases. The comparisons between simulated data and in-situ data collected in October 2007 prove that their spatial correlation waveforms agree well under the same sediment characteristics.