Abstract: To simulate the natural light-aging process of the madder on silk cultural relics, a series of systematic tests were carried out. Fluorescent UV lamp、halogen lamp and white LED were chosen in the light aging experiments. Three kinds of fading curves were gained in different irradiation of lamps, and HPLC was used to analyze the internal mechanism of the light aging of madder. The results showed that madder was destroyed seriously in the irradiation of UV light; madder faded a little slowly in the irradiation of halogen lamp than LED lamp. Purpurin was the main coloring matter in madder from Shaanxi, and the change of its area of peak in HPLC can well reflect the degree of light aging.