Abstract: CaCl2-Formid Acid (FA) system was adopted to dissolve degummed silk, the effect of Cacl2 concentration on the solubility of silk fibroin in CaCl2-FA was discussed. Rheological behavior, SEM, FTIR and XRD analyses were applied to characterize the silk fibroin (SF) solutions and films. The results indicated that the solubility was increased with the concentration of CaCl2 at the same dissolution temperature and time, and the speed of dissolution was higher at first than afterwards. The viscosity was increased first and then decreased in rheological curve when the concentration of Cacl2 was 2%,5%,8% and 10%, and the viscosity of solusion in Cacl2 concentration 1% was higher than others. Fibrillar structures were observed in the solution and films under SEM. The results of FTIR analysis were demonstrated the conformation of SF was β-sheet, and the concentration of Cacl2 was of little influence on the conformation. The structure of SF films were silk II confirmed by XRD results, and characterized by the presence of a broad peak in the 2θ scattering angle at 9.5°, 20.5° and 23.9°.