Abstract: The influence of diffusibility of disperse dyes on color fastness to ironing,soaping and rubbing of both ordinary and superfine polyester fibers was studied by color measurement.The results show that the color fastness of disperse dyes to ironing and soaping deteriorates as the diffusion coefficient of dyes increases.There is a linear relationship on the whole between the fading extent(ΔE) of dyed fabric and the diffusion coefficient of disperse dyes in ironing.The staining extent of polyester fabric in soaping is not only determined by the diffusibility of dyes,but also affected by the affinity and the state of dyes in soaping bath.The diffusibility of disperse dyes has a more remarkable influence on color fastness to ironing and soaping of superfine polyester fiber.However,the diffusibility of disperse dyes has little influence on rubbing fastness provided that the unfixed dyestuff on fabric has been entirely removed.