Abstract: A protective device and a CCFL driving system using the same are provided. The protective device employs a short detecting circuit to receive a high AC power at the high terminal of the CCFL through a step-down capacitor. The protective device outputs a short-circuit protective signal during a shorting event. A rectified diode receives high AC power through the step-down capacitor, and outputs high DC power. A first charging capacitor couples with the rectified diode, and generates a detecting voltage in response to the high DC power. An open detecting circuit, having a threshold, couples with the first charging capacitor. The open detecting circuit outputs an open-circuit protective signal when the detecting voltage is over the threshold. The protective device of the present invention has a lighting voltage-limited circuit, which couples with the first charging capacitor. The lighting voltage-limited circuit receives the detecting voltage, and outputs an over-voltage protective signal.