The experimental study on the effects of structural parameters of combustion chamber and injector, as well as EGR on combustion process, performance and emissions, was conducted on a common-rail heavy-duty(HD) diesel engine matched with two-stage turbocharger. The results of numerical simulation show that compared with CR17.5, CR16.8 and 16.2 can enhance in cylinder turbulent kinetic energy, promote the mixture of air and fuel and lead to more homogeneous mixtures. The tested results show that compared with CR17.5 and CR16.2, CR16.8 can reduce BSFC because it can enhance burning rate, shorten combustion duration. CR16.2 will lead to an increase in BSFC due to its much lower compression ratio. The results of numerical simulation and test demonstrate that NOx and soot emissions of CR17.5 are highest of all at a given EGR rate under high load conditions. However, the final soot level of CR17.5 is lower than that of CR16.2. Compared with other combustion chambers, CR16.8 can reduce soot and improve the trade-off of NOx soot due to its higher turbulent kinetic energy. The tested results concerning fuel injector matching show that relative to the fuel injector with straight holes, soot can be reduced and the trade off of NOx soot can be improved greatly via using S4 and S5, both of which have taper holes.