An illumination driving system includes a control unit and at least one base. The control unit includes a first converter and a brightness-adjustable circuit. An input AC voltage is converted into a regulated DC voltage by the first converter. The brightness-adjustable circuit is connected to the first converter. The base is separated from the control unit for supporting the at least one light-emitting device. The base includes a second converter. The second converter is connected with the first converter and the light-emitting device for converting the regulated DC voltage into an output voltage. The light-emitting device is driven to illuminate by the output voltage. The brightness-adjustable circuit generates a brightness adjusting signal to the first converter. The magnitude of the regulated DC voltage is adjusted according to the brightness adjusting signal, thereby adjusting the brightness value of at least one light-emitting device.