Abstract: The ethanol precipitation, deproteinization process and anti-oxidant activity of polysaccharides from pine needles of Cedrus deodara were studied. On the basis of single factor experiment, the concentration ratio of extraction solution, volume fraction of ethanol, and alcohol settling time were optimized by Box-Behnken design model. The optimum conditions of alcohol precipitation of C. deodara pine needles were determined by comparing the yield of polysaccharides. With the protein removal rate and polysaccharide loss rate as the index, the deproteinization effect of Sevage method and three chloroacetic acid method on polysaccharide of pine needles were compared, and the amount of reagent and the times of deproteinization were investigated. The anti-oxidant ability of the purified polysaccharides was evaluated by DPPH and ABTS free radical methods. The optimum alcohol precipitation conditions for the polysaccharide of pine needles were the concentration ratio(volume of crude extract to dry weight of pine needles) of 3:1(mL: g), the alcohol volume fraction of first order alcohol precipitation of 71%, the temperature of alcohol precipitation of 40℃, and the time of alcohol precipitation of 10 h. Under these conditions, the yield of pine needles polysaccharide was 3.81%, which was close to the predicted value. The supernatant after collecting polysaccharides was concentrated according to the ratio of solution to pine needle dry mass of 1:1(mL: g), and the volume fraction of alcohol precipitate at two level was 80%. The protein removal efficiency of Sevage method was superior to three chloroacetic acid method. Its optimum condition was that the volume ratio of Sevage reagent to polysaccharide solution was 1:1, and the number of protein removal was 3 times. After purification, the contents of primary and secondary alcohol precipitate polysaccharides were calculated by UV method with glucose conversions of 35.36% and 36.62%, respectively. The scavenging activities on DPPH and ABTS radicals were as follows: vitamin C(Vc)>secondary alcohol precipitate polysaccharides>butylated hydroxytoluene(BHT)>primary alcohol precipitates polysaccharides. The purified 80% alcohol precipitation polysaccharides of C. deodara pine needles showed good anti-oxidant activity.