A flyback boost circuit is disclosed. The flyback boost circuit includes a converter, a switch module, a driving module and an output diode. The converter includes n number of primary coils and one secondary col. The switch module includes n number of switch components. Homonymous ends of the n number of primary coils respectively connect to the n number of switch components. The other end of the n number of primary coils respectively connects to an input voltage. The homonymous ends of the secondary coil connect to a positive end of the output diode, and the other end of the secondary coil is grounded. An output capacitor is connected between a negative end of the output diode and the ground. The driving module respectively provides control signals to n number of switch components such that only one of n number of switch components is sequentially turned on within a time period for which the duty cycle ratio equals to D. A sum of the duty cycle ratio of the n number of switch components is D. Wherein n is an integer larger than or equaling to 2. In addition, the LED backlight driving circuit having the above flyback boost circuit and the liquid crystal device having the LED backlight driving circuit are disclosed.