A backlight driving circuit and a liquid crystal display device are disclosed. The backlight driving circuit is utilized for driving at least one light emitting diode bar and includes a power supply module, a conversion module, a comparison module, and a control module. The power supply module provides a driving current for the light emitting diode bar. The conversion module generates a conversion voltage according to the driving current. The comparison module compares the conversion voltage with a reference voltage. The control module controls whether the power supply module provides the driving current for the light emitting diode bar according to whether the conversion voltage is greater than the reference voltage. The backlight driving circuit and the liquid crystal display device of the present invention can limit the driving current flowing through the light emitting diode bar.