In this experimental study, measurements were made on the characteristics of evaporating steady-state fuel spray injected into a high pressure and temperature cylindrical vessel by means of an electronically controlled common rail injection system. A fuel consisting of two components, n-octane and n-hexane, having different boiling points was used to investigate the characteristics of evaporation and mixing with the surrounding gas. Fluorescence characteristics of dopants excited by the YAG laser were calibrated by means of a spectroscope having an optical fiber. From the measurement of fluorescence wavelength, we decided that fluorobenzene and diethy-methyl-amine (DEMA) in a solution of fuel. Then, two-dimensional images were analyzed for each fuel component at liquid and gas phases, simultaneously. The results show that the density and temperature of the surrounding gas are two dominant factors influencing the penetration and evaporation of the spray.