A comparative study using different fuels and nozzles has been conducted focusing on the generated density of cavitation inside diesel nozzle. In this paper a visualization experiment has been carried out and the new parameters are presented to compare the effect of the injection conditions (including injection pressure, the spray angle of nozzle, the length-diameter ratio of nozzle orifice and the fuel type) on the generated density of cavitation. The research results indicate that the generated density of cavitation is sensitive to the change of injection conditions. The generated density increases about 10% for every 10 MPa in injection pressure. The generated density increases with the increase of nozzle spray angle and with the decrease of length-diameter ratio. The cavitation appears early and changes fast by using the fuel with lower viscosity and higher saturated vapor pressure. The generated density of cavitation increases with the increase of saturated vapor pressure and decreases with the increase of viscosity. (C) 2015 Elsevier Ltd. All rights reserved.