Abstract: Caesalpinia sappan L. widely distributed in South China and Middle East Asia can be applied as a natural dye. Natural dye covers all the dyes derived from natural resources such as plants insects and animals. To change original colors produced from untreated with other chemicals, mordants have been used. This study analyzed the staining of C. sappan L. to silk fabric and color changes by chemical mordants. Each mordant was applied to the silk fabric and pH was maintained with 6 as the natural dye was extracted by boiling water. Color by the dye of dried C. sappan L. showed yellowish brown without any mordant. Except for aluminum potassium sulfate and sodium tartrate plus citric acid, silk fabric was mainly dyed in dark color by other mordants. Iron (II) sulfate-mordant induced gray and black to the silk fabric. Interestingly, copper acetate, aluminum potassium sulfate and potassium dichromate-mordants did not completely differ in color but they induced darkness and red color. Our study would be useful to comparatively analyze the staining changes by C. sappan L. dye. Further, study will be processed to evaluate them as a biological usage and other applications of natural staining.