The present invention provides a backlight keyboard with a backlight adjusting function, a backlight adjusting system and a backlight adjusting method. The backlight keyboard includes plural keys and a backlight module. The backlight module includes a light guide plate and plural light-emitting elements. The backlight adjusting method includes the following steps. Firstly, the plural light-emitting elements emit light beams, so that plural backlight zones corresponding to the plural keys are formed on the light guide plate. Then, respective luminance values of the plural backlight zones are detected. Then, an overall average luminance value of the plural backlight zones is calculated. If a preset criterion is satisfied, brightness levels of the light-emitting elements corresponding to the backlight zones are adjusted according to the luminance value of the backlight zones and the overall average luminance value.
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