Abstract: Objective To demonstrate the advantages and disadvantages of two flash point estimation methods,i.e,derivation method of vapor pressure and approximate estimation,and to show the characteristics and applicability of these two methods. Methods According to the different molar ratio of n-butyl alcohol and methanol,five types of mixed liquid were prepared and the actual flash point was measured. The difference between the measured values and estimated values obtained with these two methods was compared. Results The minimum and maximal difference between the measured values and estimated values obtained with approximate estimation was 4℃ and 1℃,respectively,while the minimum and maximal difference between measured values and estimated values obtained with derivation method of vapor pressure was 1℃ and 0℃, respectively. Conclusion The deduction method based on vapor pressure was proved more accurate than the approximate method,but the former needs more parameters for calculation.