A boost circuit for an LED (Light Emitting Diode) backlight driver circuit is disclosed; said boost circuit includes a PWM (Pulse Width Modulation) chip, a second capacitor, and a signal processing circuit. A VCC pin of the PWM chip is coupled to the input node, and the PWM chip is utilized to generate a PWM signal. One end of the second capacitor is coupled to an output pin of the PWM chip, and the second capacitor is utilized to filter out a direct current component of the PWM signal. One terminal of the signal processing circuit is coupled to the second capacitor, and another terminal thereof is coupled to a gate of the switch. The signal processing circuit is used to adjust the filtered PWM signal for generating corresponding high levels and low levels. A regulator is omitted in the present invention, therefore reducing costs.