According to the basic structure of diesel engine, 1-dimensional model of TDI diesel engine with EGR system was established. An EGR control unit was constructed using the optimum EGR rates map of diesel engine test experiment as control map of EGR control unit.Subsequently, a 1-dimensional simulation about the influence of EGR on the whole operating process of diesel engine was carried out, and it was realized that EGR rates was continuously changing with diesel engine rotate speed and load when EGR was used in diesel engine. Taking diesel engine rotate speed 1900r/min and load 10% as an example, the simulation results show that A/F ratio, cylinder pressure, the temperature in the cylinder and exhaust gas temperature are decreased and the gas mass in the cylinder is increased when EGR is used in the diesel engine. All conclusions of simulation are identical with that of the diesel engine test experiment.