Disclosed are a display backlight module and its manufacturing method. A multilayer reflector is particularly introduced into the display backlight module for a LCD display. The multilayer reflector is composed of a plurality of inter-stacked polymer films with various indexes of refraction. With introduction of interference principle, the multilayer reflector is designed to reflect or transmit the light with a specific wavelength range for acquiring a more uniform backlight. According to one of the embodiments, the display backlight module includes a backlight module, such as a direct-type or an edge-type light source. The module further includes the multilayer reflector and an optical-film module. This optical-film module optionally includes a brightness-enhancement film and a diffuser.