Introduction fiber silk consists of two main proteins which are silk fibroin and silk sericin. Silk fibroin, the fiber protein structure, is widely used in biomaterial applications particularly as sutures for decades because it has appropriate mechanical properties and slow degradability [1]. Silk sericin, the glue- proteins which silk fibroin fibers form silk cocoons, is commonly used as ingredient in various products such as cosmetics, nutrition supplements and wound products due to its ability to enhance cell attachment and proliferation [2]was reported that promoted production in wound healing process [3]. However, there are many works reported on the adverse effects of silk sericin such as immunologic stimulation and toxicity Therefore, in this study, it was interesting to clarify the cytoxicity of silk of terms attachment and proliferation of L929 mouse fibroblast cells. This study was divided into 2 parts. the investigation on the effect of sericin concentration on cell viability in the system of silk fibroin/sericin films using 2 types of silk fibroin, Bombyx mori Nangnoi Srisaket 1 and Bombyx mori nangnoi srisaket 1 and bombyx mori jul 1/1. the effect of extraction method including heat,acid,alkali and urea treatments on toxicity of sericin was also studied in the system of pure sericin films