The presence of cavitation and turbulence in a diesel injector nozzle has significant effect on the subsequent spray characteristics. However, the mechanism of the cavitating flow and its effect on the subsequent spray is unclear. The initiation, development and collapse of the cavity are strongly influenced not only by the injection pressure and back pressure but also by the nozzle geometry. The numerical simulation of cavitating flow in nozzle holes of a vertical multi-hole injector with mixture multi-phase cavitating flow model was carried out. The effects of sac geometry, hole entrance curvature radius and hole inclination angle on the cavitating flow in nozzle holes were investigated. It is finally concluded that the performance of IMPROVED nozzle is better than that of STD nozzle and VCO nozzle and small inlet turning angle of the orifice can enhance the atomization of the spray.