A self-adaptive illuminating device includes an illuminating unit, a sampling module, a sampling transformation module, a control module and a power transformation module. The sampling module samples at least one electrical property of the illuminating unit to generate a first feedback signal in response to a test signal. The sampling transformation module filters out noises off the first feedback signal for generating a second feedback signal. The control module generates an operation signal that carries at least one operational parameter of the illuminating unit in response to the second feedback signal. The power transformation module generates a drive voltage corresponding to an input voltage and the operation signal. The power transformation module drives the illuminating unit using the drive voltage.