CCD (charge-coupled device) has to work in the non-saturation area of the photoelectric conversion characteristics in the temperature measurement by two-color thermometry based on color CCD. Since the non-saturation area of CCD image sensor is narrow，the measuring range can not reach the high-temperature measurement application requirements when CCD is used to measure the temperature alone. With analysis of the CCD photoelectric conversion characteristics and the relation of radiator monochromatic radiation luminance and temperature，it is pointed out that using neutral filter can expand CCD measuring range with limited effect，but can't reach the high-temperature measurement application requirements. The experimental results prove the conclusion.