Experiments and estimation for a flash point of a emulsified fuel were made on the basis of the following a~sumption : Emulsified fuel is regarded as conjugate solution fuel consisting of two liquid phases which are partially soluble in each other. The following hecame clear : o Measured values of vapor pressure of emulsified fuels for diethyl carbonate with various internal phase ratio satisfy the assumption. o The elevation of flash point after emulsification depends on the molar fraction of oil in oil rich solution. Using this linear relation between them, it is po~sible to estimate the elevatlon of flash point with accuracy within~2'C. o The numerical calculation of the flash point of emul~ified fuel requires a study with a gas-1iquid equilibrium equation by considering activity coeffic.ient o The flash point of emulsified fuel agrees well with that of a water saturated ail fuel Measurement of flash point of emulsified fuel, therefore may be substituted with a water saturated oil fuel which is prepared easily.