The optimum processing conditions of hot water extraction of Alpinia oxyphylla polysaccharides were studied by single factor experiments and Box-Behnken design.The antioxidant activities of fruit of Alpinia oxyphylla polysaccharides were investigated using four different in vitro antioxidant assays: 1,1-diphenyl-2-picrylhydrazyl(DPPH) radical scavenging activities,reducing power,hydroxyl radical scavenging activities and chelating ability.The results showed that when the extraction parameters were controlled at liquid-to-solid ratio of 20∶ 1(mL / g),extraction temperature of 94℃,and extraction time 110 min,the polysaccharides yield could be up to 7.71%.DPPH radical scavenging activities,hydroxyl radical scavenging activities,reducing power and chelating ability of fruit of Alpinia oxyphylla polysaccharides were dependent on their concentrations.Half maximal effective concentration(EC 50) of DPPH radical scavenging activities,hydroxyl radical scavenging activities and chelating ability were(0.21 ± 0.02) g / L,(1.34 ± 0.03) g / L and(1.65 ± 0.1) g / L respectively.