A package structure of a light emitting diode for a backlight comprises a long-wavelength LED die and a short-wavelength LED die. The lights emitted from the two LED dies are mixed with the light emitted from excited fluorescent powders for serving as the backlight of a liquid crystal display. A partition plate is disposed between the two LED dies for separating them from each other. The effective light output of the package structure is increased because each of the two LED dies cannot absorb the light from the other.