Abstract: The purified technological parameters of polysaccharide extract from Lophatherum gracile Brongn was optimized, and its effect on athletic endurance was observed. The best type of macroporous resin was selected through performance comparison of static adsorption and elution experiments, then the effects of sample solution pH, sample concentration, loading speed, sample volume, volume fraction of eluent, dosage of eluent and flow rate of elution on the dynamic purification effect were analyzed. Meanwhile, purified product on the influence of athletic endurance of mice was investigated by loading swimming test and related biochemical index detection. The results showed that the optimum purification process parameters were as follows: The initial concentration of sample solution was 5 mg/mL, the sample volume was 60 mL with loading speed of 2.0 mL/min, the pH value of sample solution was 5.0, and the volume fraction of ethanol was 80%, the eluent volume was 160 mL with flow rate of 1.0 mL/min. The purity of polysaccharide in product increased from 16.39% to 57.35%. Compared with the blank control group, the purified product groups at middle and high doses significantly prolonged exhaustive swimming time (P<0.05, P<0.01), enhanced activity of lactic dehydrogenase(P<0.05, P<0.01), decreased lactic acid and urea nitrogen content (P<0.05, P<0.01) after exercise. Therefore, polysaccharide of Lophatherum gracile Brongn. could preferably improve athletic endurance in body.