Internal solitary waves usually transform into an internal wave train when propagating through the continental shelf/slope. However, such phenomenon is rarely taken into account in previous design of marine structures. This paper aims to construct an evolution model to describe the evolution of internal wave trains. To be specific, in consideration of various influential factors, such as benthic topography, friction, dissipation, et al., a mathematical model is built to describe the evolution of wave trains and numerical experiments are carried out to validate the method by analyzing the leading internal wave and the induced velocity fields. It is shown that the numerical results of the wave train displacement and the velocity fields are in good agreements with the observational data in South China Sea. In the meantime, the sensitivity of dissipation and friction to the model is discussed.