以大米蛋白粉为原料，通过二步酶解法制备大米低聚肽，在对其基础理化成分分析的基础上，利用氨基酸组成、相对分子质量分布、扫描电镜、紫外光谱和圆二色光谱分析进行结构表征，采用羟基自由基清除能力、铁离子还原能力（FRAP）、氧自由基吸收能力（ORAC）和还原能力4种体外抗氧化评价体系考察其体外抗氧化作用。结果表明：大米低聚肽中蛋白质和肽含量分别为95.75%±0.53%和89.11%±0.94%；大米低聚肽富含亮氨酸、丙氨酸、缬氨酸等抗氧化性氨基酸，相对分子质量在1000以下的组分占91.84%；大米低聚肽为明显的球体颗粒状，表面有不规则褶皱和气孔，在270nm波长处有最大吸收峰；二级结构以多种构象并存，α-螺旋、平行式β-折叠、反平行式β-折叠、β-转角和无规则卷曲含量分别为6.0%±0.3%、3.3%±0.2%、40.2%±1.9%、19.5%±1.0%和32.1%±2.5%；大米低聚肽对羟基自由基的半抑制浓度（IC50值）约为11.1g/L，ORAC值为（498.88±18.29）μmol/g（以Trolox为标准品计），质量浓度为15.0g/L时的FRAP值与0.04g/L的阳性对照Vc相当，质量浓度为15.0g/L时的还原能力与0.05g/L的Vc相当。

Rice oligopeptides were prepared from rice protein powder by two-step enzymatic hydrolysis.Based on the analysis of their basic physical and chemical components，the structure of rice oligopeptides was characterized by amino acid composition，relative molecular weight distribution，scanning electron microscopy，ultraviolet spectrum  and circular dichroism.The in vitro antioxidant activity of rice oligopeptides was investigated by four index of in vitro antioxidant evaluation system including hydroxyl radical scavenging ability，ferric ion reducing antioxidant power （FRAP），oxygen radical absorbance capacity （ORAC） and reduction capacity.The results show that： the protein and peptide contents in rice oligopeptides are 95.75%±0.53% and 89.11%±0.94%；rice oligopeptides are rich in antioxidant amino acids such as leucine，alanine and valine，and the components with relative molecular weight less than 1000 accounted for 91.84%；rice oligopeptides are obvious spherical granules，and have irregular folds and pores on the surface；the maximum absorption peak appears at 270 nm wavelength；the contents of α-helix，parallel β-fold，antiparallel β-fold，β-turn and random coil are 6.0%±0.3%，3.3%±0.2%，40.2%±1.9%，19.5%±1.0%，and 32.1%±2.5%，respectively.The IC50 value of rice oligopeptides to hydroxyl free radical is about 11.1g/L，and ORAC value is （498.88±18.29） μmol/g （with Trolox as the standard）；the FRAP value of rice oligopeptides at 15.0g/L is equivalent to that of 0.04g/L positive control Vc，and the redu-cing ability of rice oligopeptides at 15.0g/L is equivalent to that of 0.05g/L Vc.