This study was aimed to study the surface morphology of Eri (Samia ricini) silk cocoons collected from different sources called China, Chaingmai, Lampoon, SIC (Silk Innovation Center) and Thai varieties. All of Eri silk fibers were prepared by hand. They were studied under scanning electron microscope (SEM) for morphological observation. The cross-section images showed China has composed of porous structures in higher ratios than Chaingmai and Lampoon, respectively. In contrast, SIC and Thai composed of nonporous structures. In addition, the effect of different organic solvents on each Eri silk fiber was also investigated. Eri silk fibers were treated with methanol, ethanol, ethyl acetate and methyl acetate in different incubation times and concentrations before examining with attenuated total reflection infrared (ATR-IR) spectroscopy. The results found that methanol showed the highest effect to change the structure of Eri fibers, compared to ethanol. Ethyl acetate and methyl acetate showed similar activity to enhance β-sheet form and lower than that of methanol and ethanol, respectively. The methanol concentrations and incubation times which suitable for China, Chaingmai, Lampoon, SIC and Thai were 40% (3 h), 40% (2 h), 60% (1 h), 60% (3 h) and 60% (3 h), respectively. From the results, SIC and Thai were considered as higher strength than those of China, Chaingmai and Lampoon. This was due to the fiber of the last group composed of porous structures in higher ratios than that of first group.