A method of measuring LED junction temperature includes the steps of: (a) obtaining a temperature curve of an LED; (b) inputting at least one rated AC voltage to the LED; (c) measuring a temperature at a specific point on an outer packaging structure of the LED, putting the temperature measured at the specific point into the temperature curve, and calculating a junction temperature of the LED by interpolation; and (d) substituting the result from the calculation in the step (c) into a numerical analysis model to obtain temperature oscillation of the LED.