The detection of deterioration degree of ancient silk fabrics will be helpful to the selection and developing of conservation methods. This paper carried out some research on the deterioration extent and mechanism of silk fabrics by means of infrared spectrometry. The samples artificially aged and excavated from Hubei, Innermongolia and Qinghai province, were analyzed. The artificially aging was done by simulating three main natural aging factors: light, heat and hydrolysis. The infrared spectrometric analysis results show that although the infrared spectrometry is a half-quantitative analysis method, for the hydrolysis-aged silk fabrics, it can give good qualitative and better half-quantitative analysis results because of the increase of carboxyl. So the infrared spectrometric analysis is of practical value for the conservation state and aging mechanism studies of ancient silk.