Exhaust Gas Recirculation (EGR) is a small portion of the exhaust gas produced by a diesel engine or a gasoline engine. EGR will reduce the total emissions of flow (mass), so the total pollutant output in the exhaust gas emissions will be reduced relatively. The task of the EGR system is to make the recycling of the waste gas in every working point to achieve the best condition, so that the combustion process is always in the most ideal situation, and ultimately ensure that the emissions of pollution in the lowest.