Abstract: Aiming at the poor dyeing property of the cotton/milk protein fiber blended yarn, the effects of process factors such as dyestuff, resist agent, pH value, dyeing temperature and time on its homochromatism were discussed. The optimum process of one-bath dyeing of cotton/milk protein fiber blended yarn with reactive dyes was determined through orthogonal experiments. The results indicate that the blended yarns have obtained good homochromatism and high dye-uptake when one-bath dyeing of the yarns was performed with pH value= 8, resist agent 0.8g/L and trichromatic reactive dyes such as Red CN-7B、Blue CN-BL and Yellow CN-603 at 70°C for 40 min.