Silk is mainly used in the textile industry. Recently, the use of silk has expanded to cosmetic and food industry. However, basic research on the nutritional effect of silkpowder has little conducted. Previously, we reported that silk fibroin from Bombyx mori lowers the serum cholesterol level. But the effect of silk powder on lipid metabolism and the difference of Bombyx mori or Antheraea pernyi were not clear, Therefore, we examined the effects of silk powder from Bombyx mori or Antheraea pernyi on defecation and fecal fat excretion, using the SD rats fed on high fat diets. We made three groups fed on different kinds of high fat diets: the basic one, the one containing the silk powder from Bombyx mori (5% add), and silk powder from Antheraea pernyi (5% add).There were no significant differences in the body weight or food intake among the3 groups. The plasma total cholesterol and triglyceride level have no significant effect.Interestingly, in the group fed on the silk powder, the feces and fecal triglyceride and bile acid increased significantly, and color of feces was white, suggested silk powder has effect on fecal excretion.These results may explain the effect of Silk protein on lipid metabolism.