A lamp driving device with an open voltage control comprises a DC power source, a square wave switch, a square wave controller, an LC resonant circuit, a driver transformer and a current detector; wherein the square wave switch outputs a square wave signal to the LC resonant circuit, the LC resonant circuit converts the square wave signal into a sinusoidal wave signal and outputs the sinusoidal wave signal to the driver transformer, and finally the driver transformer drives the lamp and the current detector is used to detect the operation of the lamp, and, if the lamp is found open-circuit, a PWM control pin will control the square wave controller to stop the operation of the lamp driving device, thereby enhancing safety in using the lamp.