The present paper did some researches on the deterioration mechanism and the changes in crystallinity of silk fabrics by means of the X-ray diffraction analysis. The samples artificially aged and excavated from Hubei,Innermongolia,Shaanxi and Qinghai provinces were analyzed. The artificial aging was done by simulating three main natural aging factors,light,heat and hydrolysis. The analytical results show that X-ray diffraction analysis could reveal the aging process and characteristic of silk,as well as the changes in crystallinity during silk aging. The X-ray diffraction analysis is of practical value for the conservation state and aging mechanism studies of ancient silk. In addition,X-ray diffraction analysis could also provide important informaton on ancient technology of textile and apparel.