[目的]对3,5-二硝基水杨酸(DNS)光度法测定淀粉多糖的影响因素进行研究,并用该法测定甘薯中淀粉多糖含量。[方法]甘薯经洗净、晾干、去皮、捣碎匀浆后,用85%的乙醇沉淀淀粉多糖,沉淀加入30mlHCl(6mol/L)和100ml水于沸水浴水解2h后,以DNS光度法显色,520nm下比色测定。[结果]本法标准曲线回归方程A=0.2842C-0.07,r=0.999,线性范围为1～120μg/ml。相对标准偏差为1.57%,检出限为1μg/ml,样品最低检出浓度0.23%。测定了20个不同品种和产地甘薯中淀粉多糖含量,结果所测样品中淀粉多糖含量范围为9.76%～29.21%。[结论]该法具有简便、安全、易于操作、结果准确精密,适合于批量甘薯中淀粉多糖含量的测定。 [Objective] The research aimed to study the influential factors of starch polysaccharide by 3,5-dinitrosalicylic acid (DNS) spectrophotometry and to determine the content of starch polysaccharides in sweet potato by this method. [Method] The sweet potato was washed, dried, peeled and homogenized. After the starch polysaccharide was precipitated with 85% ethanol, 30ml of HCl (6mol / L) and 100ml of water were precipitated and hydrolyzed in boiling water bath for 2h. Color, 520nm colorimetric assay. [Results] The regression curve of this standard curve A = 0.2842C-0.07, r = 0.999, linear range of 1 ~ 120μg / ml. The relative standard deviation was 1.57%, the detection limit was 1μg / ml and the lowest detection limit was 0.23%. The content of starch polysaccharides in sweet potato of 20 different cultivars and producing areas were determined. The content of starch polysaccharides in the tested samples ranged from 9.76% to 29.21%. [Conclusion] The method was simple, safe and easy to operate with accurate and precise results. It was suitable for the determination of starch polysaccharide in batch sweet potatoes.