Alternative fuels, such as gaseous fuels and oxygenated fuels etc., have been used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility, and flash-boiling takes place easily in the fuel spray. It is been known that the flashing is a favorable mechanism for atomizing liquid fuels. However, flash-boiling process in a engine is hardly studied. In this study, the sub models for flash-boiling spray of multicomponent fuel which take account for properties, vaporization process, bubble nucleation, growth and disruption in multicomponent fuel droplet were added to KIVA3V. The flashing spray characteristics from numerical simulation qualitatively showed good agreement with the experimental results. In addition, it was confirmed that flash-boiling effectively accelerated the atomization and vaporization of fuel droplets.