In dyeing of wool, one of the most important factors is to control the initial dye absorption. Thus we use a levelling agent to prevent rapid dyeing in initial stage. But increasing the amount of surfactant results in low final adsorption. So we find the optimum concentration of surfactant inter-acting to the dye. In this study, we estimated the optimum ratio of dye and surfactant, when using mixed nonionic and anionic surfactants. We examined the influence of pH, concentrations of dye and surfactant, and liquor ratio on dye exhaustion under real dyeing conditions. Due to the complexity of this subject, a central composite plan has been used. The results gave numerically analytical values and possible mechanism of the dyeing process. Then we found the optimum condition by calculation based on the proposed equation and, when applied to real experiments, the experimental results are very well fitted to the calulated data.