Large quantity of metal mordant in natural dyeing has been used. For environmental reason, there is a need to reduce the amount of metal mordant and suggest the optimum amount of metal mordant in dyeing process. In this study, the relationship between mordant concentration and dyeing property was investigated. Various metal mordant concentrations of AI, Cu, Fe, Sn, were studied (from 1 to 5%). After treatment of mordant on cotton fabric, the concentration of metal ion in used mordant solution was quantified. There was no significant difference of the tone of color in mordant concentration from 1% to 5%, Therefore, there is no need to increase mordant concentration over 1%. chitosan treated cotton fabric showed a significant increase in dyeing affinity compared to untreated cotton fabric (the value of ${Delta}E$ was 20). chitosan increased dye affinity significantly in the presence of mordant. It can be suggested that chitosan itself can replace metal mordants in the future.