Experimental work has been performed to characterized diesel spray combustion in an optically accessible constant-volume combustion vessel. A single-hole diesel injector with nozzle diameter of 100 um has been used for testing. Bulk gas temperature and density with the combustion vessel has been prepared at specified diesel engine condition (900 K, 23.9 kg/m3) with a pre-burn process. A Z-type schlieren system with high-speed imaging was set up for spray visualization. Diesel combustion characteristics including ignition delay, location of ignition and liquid lengh are compared under different fuel onjection pressures and different fuel including Green diesel.