The two-stroke marine engine have higher NOx emission for its low rotational speed. However, the limited can be improved for the NOx emission in recent years. The large size of the two-stroke marine engine makes the use of experimental techniques, the investigate this potential, expensive and time consuming. The computational fluid dynamic (CFD) model of two-stroke marine diesel engines can be built in this article. The model is valeted with the results of experiment. The in-cylinder pressure is agreement with that of experiment. The error located in the acceptable range for the emission products, NOx, CO, HC and CO2. This model can be used in the simulated the performance of two-stroke marine diesel engines using EGR. Four different EGR ratio can be simulated in this article, for example 10%, 20%, 30% and 40%. The in-cylinder pressure, temperature, specific fuel consumption, power and the quantity of emission product can be compared for different EGR ratio. The quantity of NOx reduced with the increasing of EGR ratio, which can be to achieve the requirements of NOx emission legislation (Tier Ⅲ). The varies of specific fuel consumption is not obvious for the increasing of EGR ratio, because, the air-fuel ratio is large for the two-stroke marine engine. The ignition delay time and the combustion duration time increase with the increasing of EGR ratio. The maximum combustion pressure decrease and the maximum heat release rate also decrease with the incising of EGR ratio. The EGR techniques have large potential to reduce the NOx emission.