A light emitting diode (LED) illuminant system, a manufacture method thereof, and a backlight module using the same are provided. The LED illuminant system includes a plurality of white light illuminants and at least one green light illuminant mixed in the white light illuminants. A light power ratio of the green light illuminant to the white light illuminants is in between ⅕ to 1/20. The color temperature of the whole illuminant system will be enhanced to a certain extent by mixing the green light illuminant and the white light illuminants. The manufacture method includes the following steps: obtaining a transmission spectrum of the white light illuminants; analyzing the transmission spectrum to determine n supplemental amount of a green light; and disposing at least one green illuminant in accordance with the supplemental amount of the green light.