Abstract: LaFond et al. (1962) advocated the opposite direction of internal wave propagation and sediment transport during the formation of internal wave and internal tide deposits. In the light of the fluctuation theory of internal wave and the marine physics, the present paper gives a quantitative explanation of the propagation of the internal wave by formulating the fluctuation equations of two-layer model on the water interface of different densities. According to the expression of quantitative explanation, when internal wave travels along the two-layer water interface of different densities, the horizontal directions are opposite between the two-layer internal waves, which keep the circulation quantity across the seafloor to be zero. Under the density interface, the moving direction of internal wave at wave trough is opposite to the progresive direction. Compared with the wave crest, the wave trough is closer to submarine, and the section at wave trough is smaller. Therefore the velocity under the wave trough is faster than that under the wave crest. This may easily cause the unidirectional superior flow in the opposite direction with the internal wave progression and the overall trend of the sediment transported by the unidirectional superior flow is in the opposite direction to the progression of internal wave.