Abstract: This study aims to prepare silk fibroin film of Eri (Philosamia ricini) and investigate their conformational structure and thermal properties after treating with methyl alcohol. The Eri silk fibroin solution was obtained by dissolving the Eri cocoons with 9 M Ca(NO3)2. The silk fibroin hydrolysate was dialyzed to remove the concentrated salt against distilled water. It was then concentrated to give 2% silk fibroin by weight. Ten milliliter diluted silk fibroin to 0.5% weight per polystyrene plate was used to cast film at room temperature for 2 days. The obtained films were then treated with 80% methyl alcohol with different times. They were subjected to investigate using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyzer for conformational and thermal studies, respectively. The FT-IR spectra showed that Eri silk films were composed of both α-helix and β-sheet structures before exposure to alcohol and changed from low content of β-sheet structure to higher ratio when immersed in alcohol. In addition, the β-sheet structure gradually increased according to the increase of treating time used. The relative data were obtained from thermal investigation since the decomposition temperatures of Eri silk fibroin films were increased as follow by the increase of methyl alcohol treating time. It is promising that methyl alcohol can be affected to change both conformation and thermal behavior of the Eri silk fibroin film.