A method measures chromaticity values using a colorimeter to solve the drawbacks of conventional technologies, such as an inaccurate illuminant, the filter of color-matching function being difficult to be deposited and manufactured within a filter mod colorimeter, and using an expensive spectrometer within a spectrum mode colorimeter. The spectrometer and the filter of color-matching function is not needed, and an accurate chromaticity value of an object by using a multi-band illuminant illuminating the object and a power meter. Further, the multi-band illuminant can adjust the illumination condition of a standard illuminator under different color temperatures, and the chromaticity values of the object can be measured under different color temperatures. The accuracy of the measured chromaticity values is up to the level of the spectrum mode colorimeter, and the price is less than the spectrum mode colorimeter.