The effects of decoloring agent PS-10 on rosin were studied. Based On results of single-factor test, the official experiment was initiated. In the experiment, the effects of three factors:temperature of reaction, time of reaction, and dosage of decoloring agent, were analyzed using the mathematical mode-"Quadratic Orthogonal Rotable Combination Design". Regression equations were also developed. Using the theory of optimization, the following optimum conditions of experiment were determined: temperature of reaction 272～C, time of reaction 4h,and dosage of deeoloring agent 0. 175%. Results from the proving test are color 120 Hazen,AV 167.2 mg/g,SP 76.1℃, which accorded with the demands of quality of light-colored rosin.