The numerical models of phytoplankton dynamics can reproduce the spatial and temporal variation of alge and quantify the contributions of all physical and biological processes involved in phytoplankton production. It takes a great role when studying the eutrophication of coastal sea. A brief review on the model’s development is given. Time dependent water column model is the initial state of physical biological couplling. Vertical resolved model, horizontal box model and three dimensional model can simulate the annual cycle of biomass. Short term model studies show a great importance of the short time physical processes to the evolution of marine ecosystem. More nutrients and function groups are included in the eutrophyication models. They must reproduce the variation of phytoplankton biomass at first. Then the response of the sea to the strategy of nutrient deduction can be investigated. More attention should be pay on the driven and boundary processes in our modelling studies.