Theoretical equation to evaluate the effect of temperature on the flammability limits of pure hydrocarbons was proposed in present study and compared with other methods available in the literatures. Theoretical equation was based on the thermal theory. Verification of the linear equation has been implemented on the cases of hydrogen, methane, propane, propylene, butylene, pentane and isobutane. The equation in this paper shows an average absolute relative error of 0.43% and 0.93% for lower and upper flammability limits, respectively. The equation possesses better prediction accuracy than other available methods at UFL. The reason for better accuracy is that the simple chemical kinetics about oxygen consumption was used to calculate reaction heat at upper flammability limit. Finally, the temperature range of application of theoretical equation was discussed in detail.