An upgraded multizone model is developed in order to study the effects of fuel injection characteristics on DI diesel engine soot and NOx emissions. Effects of fuel spray characteristics, the movement and evaporation of droplet, and spray wall impingement are considered. NOx emission is predicted by the extended Zeldovich mechanism and soot emission is simulated by the current soot formation and oxidation model. The multizone model can be used to calculate cylinder pressure, heat release rate, engine performance, NOx and soot emissions, etc.In this paper, the boot injection and split injection are simulated. The simulation shows that the fuel injection characteristics have significant effects on the process of engine combustion and emissions. The NOx and PM emissions from DI diesel engine can be reduced simultaneously by optimizing the shape of injection rate, especially by boot injection.