This study is performed to investigate the effect of the mordant and chitosan on the colorfastness to laundering and physical properties of the mordanted, chitosan treated and natural - dyed cotton, silk and acrylics substrates. Natural dyes are extracted from Gromwell by boiled water. Three different compounds of Al, Cu, Sn and Chitosan are used as mordanting agents. The result of this study is summarized as follows: 1. Color of the fabrics dyed with Gromwell changes redder, bluer and darker after chitosan treated and mordanting. 2. After washing, the color of natural dyes changes more light and gray, Chitosan and Cu mordanting gives better colorfastness in washing than any others. 3. All chitosan treated fabrics improve air permeability. 4. In the chitosan treated fabrics, a half life of the static electricity is shown good result.