The invention provides a backlight module, using blue backlight to excite the red, green QD films to obtain red and green fluorescence; and disposing two metal wire grids on both sides of the green QD film to form a Fabry-Perot cavity, the Fabry-Perot cavity able to select and enhance luminance intensity of a specific wavelength selected from the green light emitted by the green QD film so as to improve color purity and luminous intensity of the green light, and thus increase the color gamut of the backlight module, as well as improve the luminous efficiency of the green QD film, and significantly improve the low efficiency problem of fluorescence QD film. Moreover, the metal wire grid may form a brightness enhancing structure with the reflective layer of the backlight module to save setting up a brightness enhancing structure and reduce the thickness of the backlight module.