The dye-resist effect of reactive dye-resist agents in reactive dyeing of silk was investigated. The dichlorotriazine-based dye-resists achieved a higher effectiveness than others since they make a charge barrier of diffusion in the silk fiber periphery due to high reactivity of dichlorotriazine group. Similarly, in the case of hetero-multifunctional dye-resist agent, the dye-resist agent containing both a dichlorotriazine and an ${alpha}$-bromoacrylamide reactive groups achieved better resist effectiveness than those containing both a monochlorotriazine and an ${alpha}$-bromoacrylamide groups. Also, their resist effectiveness was improved by increasing the number of sulfonate groups in the dye-resist agents and the number of reactive groups in the reactive dyes applied to them.