Abstract: Based on a description of the combustion process, BOOST code is used to model the emission characteristics of a turbocharged direct injection （DI） diesel engine. The calculated results show a good accordance with the measurements. Furthermore, the results at rated speed as have been by FIRE code are analyzed. Finally, the effects on the emission control of DI diesel engine are discussed. The results show that the earlier the injection angles the more NO_x emission, and the less the amount of SOOT produced.