For improvement of diesel combustion and emissions by ethanol intake port injection for the promotion of premixing of the in-cylinder injected diesel fuel, and by increased EGR for the reduction of combustion temperature. This research investigated improvements of diesel combustion and emissions by ethanol intake port injection for the promotion of premixing of the in-cylinder injected diesel fuel with sufficient ignition delay, and by increased EGR for the reduction of combustion temperatures. The results show that the smoke emissions were reduced with promotion of premixing with ethanol port injection, maintaining low NOx by EGR. It was revealed that the compression ratio should be reduced to promote premixing of the diesel fuel with ethanol as long as misfiring and knocking do not occur. The combination of premixed ethanol and EGR can achieve smokeless and ultra low NOx combustion even with the fuel injection pressure of 60 MPa.