Abstract: Nonlinear internal wave effect on the long range low frequency reverberation is studied in shallow water. Fluctuation of sound energy propagation from sound source to scattering element of seabed and from scattering element to receiver caused by nonlinear internal wave is analyzed,which caused fluctuation of long range reverberation.A model of normal modes reverberation with nonlinear internal wave in shallow water is given in this paper.Using a nonlinear internal wave sample,internal wave effect on long range low frequency reverberation was numerical simulated. Numerical simulation results show that the nonlinear internal wave can lead long range reverberation to boost.Normal mode coupling caused by this nonlinear wave was analyzed and the reason of range reverberation enhanced was given.