This standard applies to the evaluation of the color fastness of wood products to light under Dss Light source. The principle is to use artificial Light source equipment simulating 8 light irradiation conditions to expose wood samples and a set of blue wool master standards, and then use the blue wool master standard to compare with the grey sample card for evaluating discoloration to obtain the color difference grade. By regularly using a colorimeter to determine the color index of wood product samples during exposure, and calculate the color difference value of the sample before and after exposure to the sun. According to the comparison of the color difference and the colour fastness level of the grey sample card, the color fastness level of wood product samples is determined.