The purpose of this study was to investigate the dyeability and color fastness of cotton and silk fabrics dyed with extract of Arrowroot leaf princeps. The experimental items were divided into the mordant treatment, component of fabric and kind of mordants. The experimental study was done by laundering, abrasion(dry/wet), perspiration(acid/alkali), light fastness, color difference by C.C.M system and K/S test. The summerized finding reulted from experiment and investigation are suggested as follows : In the C.C.M and K/S test on mordanting method and kind of fabric, that of silk and cotton was the most effective in the pre mordant treatment. In the C.C.M and K/S analysis on 5 mordants, that of silk and cotton was significantly improved when mordants was treatmented. Especially, that of Fe mordanting treatment was higher than Al, Cu, Cr and none. In color fastness on mordants, laundering, perspiration and abrasion fastness showed 4-5 grade but light fastness showed 1-3 grade.