The density profile of sea water is a crucial environmental factor affecting the generation and evolution of internal waves. The density profile is usually modeled with hyperbolic tangent function, however it does not work well when it is used to model density profile with a shape like ^"7^", which is common in ocean. In the present paper, the commonly used hyperbolic tangent density profile model is modified by introducing a correction coefficient. The modified model, inheriting the merits of the original model, can well describe the characteristics of thermocline and is much more accurate than the original model. Application of the modified model in global oceans demonstrates that it can be widely used to model sea water density profile.