It is necessary to assess the current conditions of silk textiles before a conservator starts a conservation job. Scanning electron microscopy (SEM),Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG) and amino acid analysis (AA) were used to characterize and compare modern silk and Tang Dynasty beige silk socks from Astana tombs．The Astana silk socks were very fragile when compared with modern silks. It was found that the appearance and molecular structure of the Tang Dynasty silk socks had changed significantly. The appearance of fiber was rougher and the texture was less compact. The thermal decomposition temperature of ancient silk dropped. In addition, the amino acid composition changed significantly, too. In particular, the aspartic acid and tyrosine content were about 30% lower. The textile had also lost its strength. The results indicated that the current state of preservation of the silk stocks is not satisfactory and that immediate conservation is needed.