Abstract: Disclosed is a lamp-tube driving device including a controller, an oscillating circuit, a converter, and a protective circuit. Connection relations there-between include the oscillating circuit coupled to the controller, the converter coupled to the controller and CCFL, and the protective circuit coupled to the CCFL and oscillating circuit. The controller is activated in response to first input voltage, and configured to output a control signal in response to second input voltage. The oscillating circuit is able to adjust oscillating frequency of operation clock for the controller. The converter is controlled with the control signal, and configured to convert third input voltage into an output voltage. This output voltage is for driving the CCFL. The protective circuit disables the oscillating circuit when the CCFL remains at a state such as open circuit or short circuit. A lamp-tube module and a lamp-tube driving system for the lamp-tube driving device are further disclosed.