In diesel engines, diesel nozzle with micro-orifices has great effect on fuel spray characteristics, and then it additionally affect engine performance, fuel consumption and emission formation.Actually, the internal flow of diesel fuel inside the nozzle, the spray breakup and the atomization have tremendous dependence on the nozzle internal geometries, which however, are difficult to be researched and analyzed before.Based on the synchrotron X-ray micro-tomography provided by Shanghai Synchrotron Radiation Facility, customized single-hole diesel nozzles were measured and three-dimensional models of these nozzles were established.Internal geometries, such as the diameter, the length and the inlet curvature radius of orifice, can be measured, making it possible to analyze the impact of different processing methods on nozzles, and therefore, the manufacturing defects can be detected directly.Meanwhile, the nozzle digital models were successfully exported to CFD software to simulate the internal flow of high pressure fuel inside the nozzle;the effects of nozzle geometries on internal flow characteristics have also been analyzed.These works are significant to the promoting of diesel nozzle processing technologies, and to the revealing of high pressure fuel spray breakup mechanism.