Diesel Engines have an advantage in CO_2 emission, however NOx and PM (Participate Matter) need to be reduced. EGR is an effective technique of emission reduction. This experimental study of emission reduction looks into cooled EGR effects by using high-boosted single cylinder engine. Boost-pressure sets just as 6-cylinder turbo diesel engine then extends until 351.3kPa. There are slight little influences on Engine performance by EGR. NOx reduction of 80% was achieved by 30% EGR ratio at wide range load of the engine. EGR is also practical to decrease PM emission under the condition of high air excess ratio and low smoke.