Abstract: A theoretical prediction formula for the average intensity of reverberation caused by the ice layer is given for the operation of bistatic sonar underneath the ice with small-scale roughness.Firstly,the Arctic ice layer is equivalent to an elastic medium with a rough interface,and the three-dimensional scattering intensity model of the rough ice layer is established based on the fine fitting roughness spectrum.Then a three-dimensional bistatic sonar geometric model is established to determine the effective scattering region.Finally,the calculation formula of the average intensity of the bistatic ice reverberation is given,and in the case of this fitted roughness spectrum,the prediction formula is used to calculate the examples of the effects of sonar configuration parameters,sea ice physical properties and acoustic properties on the reverberation intensity under ice.The numerical simulation results show that the formula can estimate the average reverberation intensity of the bistatic sonar underneath the Arctic ice,and the influences of sea ice physical parameters and sonar configuration parameters on the reverberation intensity are analyzed.The configuration parameters of the sonar mainly affect the effective area of the scattering,and the physical parameters of the sea ice affect the scattering intensity of the ice layer.Moreover,the ice layer sound speed ratio not only affects the reverberation intensity,but also affects the decay speed of the reverberation.