The powdered activated carbon was used as discoloring agent for decolorization in the separation of L-lactic acid.The mathematical regression models between the total discoloration efficiency rate and its influencing factors were attained by the combination design of quadratic orthogonal rotation based on the results of the single-factor design.The software Matlab was used to draw response surface and analyze the effects of technology parameters on the total efficiency rate of discoloraization.The optimum process parameters were:activated carbon 0.318 %,discoloring temperature 43.18 ℃ and discoloring time 18.83 min.Frequency analytical method showed that optimum conditions for 95 % probability of obtaining 70 % discolorization were:activated carbon 0.395-0.695 %,discoloring temperature 56.88-69.84 ℃,and discoloring time 15.68-22.58 min.The study provided a foundational consult to choose operating parameters for decolorization in the separation of L-lactic acid.