The dyeing powder drawn out from Cinnamoum cassia by water was concentrated. Using this powder, the silk fabrics were dyed and they measured with the K/S value, surface color, dye fastness and antimicrobial properties. The colorant of Cinnamoum cassia was proved flavonoids by FT-IR spectrum. The K/S values of silk by mordants concentration were much higher than those of high-concentration, the color yield of the silk fabrics were most efficient the premordanting method. The surface colors on the dyed fabric depended heavily upon mordants used or mordanting methods. For all cases, the value of the dyed fabric was generally dark except AI-mordant. The chroma produced clear for the unmordanting, the color difference was distinct when using the Fe-mordant. The color fastness was significantly improved when mordants were added. In the case of the light fastness, Cu-mordants improved more than 1-2 level. The Cu-mordant showed the greatest antimicrobial activity on the silk fabric.