A method and apparatus for calibrating color temperature of color display devices aims to calibrate output bases of RGB three original color lights of a color display device so that different color display devices can radiate the same color temperature in the same color temperature settings. The method of the invention uses a colorimeter to obtain current chromaticity value radiated from the color display device in a standard color representation system and in the condition of known output bases of the current three original color light signals, and through calculation to obtain the proportional relationship of the current radiating color temperature and an objective color temperature in the same standard color representation system, and based on which to derive the output bases of the required three original color light signals corresponding to the objective color temperature to be calibrated. The results are written through the apparatus into a color profile of the color display device.