Abstract: A backlight driving circuit and a liquid crystal display device are described. The backlight driving circuit drives at least one LED bar and includes a power supply module, a switch module, and a detection module. When the detection module detects that a positive polarity end of a power supply voltage of the power supply module is electrically coupled to a negative polarity end of the LED bar, the switch module switches the positive polarity end of the power supply voltage to be electrically coupled to the positive polarity end of the LED bar and switches a negative polarity end of the power supply voltage to be electrically coupled to a negative polarity end of the LED bar. The present invention can detect the polarities of the LED bar so that the LED bar can keep on working normally.