A orthogonal test was utilized to optimize the ultrasonic-assisted extraction process of the polysaccharide in Ardisia mamillata based on the single-factor experiment, and its antioxidant activity was evaluated. The results demonstrated that the polysaccharide in Ardisia mamillata could be extracted best by using distilled water as the extracting agent, with the solid-liquid ratio 115（g/mL）was treated , ultrasonated at 65 ℃ for 20 min, for 4 times. Thus the extracting rate of the polysaccharide from Ardisia mamillata was (3.42±0.28) mg/g. Moreover, it was also found that the polysaccharide form Ardisia mamillata possessed good antioxidant activity. It was tested that the polysaccharide showed stronger clear ability of DPPH than that of BHT at concentration 4 mg/mL, and 0.5% polysaccharide had comparable antioxidant effect on lard with that of BHT.