A luminance compensation method is provided. The luminance compensation method includes: establishing a time-varying luminance sequence according to an average luminance value of a plurality of sampled display devices in each unit time during an initial start-up period; establishing an operating luminance sequence according to an average operating luminance value of the sampled display devices under a plurality of different driving condition values after the initial start-up period; generating a driving condition value look-up table according to the time-varying luminance sequence and the operating luminance sequence; and obtaining compensation driving condition values in each unit time according to the driving condition value look-up table and the time-varying luminance sequence and accordingly establishing a time-varying compensation sequence, such that a display device drives a backlight module according to the time-varying compensation sequence in each time unit during the initial start-up period.