A LED backlight driving circuit includes a voltage boosting circuit for converting an input voltage into an output voltage for a LED string; a current control module connected to a negative terminal of the LED string and for regulating a working current of the LED string; a driver chip for supplying the voltage boost circuit and current control module respectively with first and second square wave signals; a current detection module for detecting the working current of the LED string to generate detection signal; a control signal module for receiving the detection signal to generate a control signal; and a frequency regulation module for receiving the control signal to thereby generate a resistance. The frequency regulation module connects the driver chip, and the driver chip regulates a driving frequency of the driving circuit according to the resistance. A LCD device using the driving circuit also is provided.