Based on the runoff process series of 1956-2011 of Tangnaihai Station in the Upper Yellow River, the annual distribution and inter⁃annual varying characteristics of the historical runoff process was analyzed and the trend and periodicity of the runoff process series were discussed by applying the linear trend estimation and maximum entropy spectral analysis method in this paper. The results show that a) the annual distribution of runoff process in the upper Yellow River varies obviously and the runoff in summer flood period ( from July to October) accounts for 60%;b) the amount of wet and special rainy year accounts for 48.21% among the research periods, the ratio for the maximum and the minimum annual runoff is 3. 08 and the runoff process presents a weak decreasing trend, which is useful for the comprehensively development of water resources in the upper Yellow River;c) the runoff process in the Upper Yellow River has an obvious cycle periods of 28 a, 8 a and 5 a.%以黄河上游唐乃亥水文站1956—2011年径流量资料为基础，分析了年内、年际径流量的变化特征，采用线性倾向估计法和极大熵谱分析法对径流量序列的趋势性和周期性进行了识别。结果表明：①黄河上游径流量年内分配差异明显，径流量主要集中在7—10月，7—10月径流量占全年径流总量的60％；②研究时段内丰水／特丰年份占整个序列长度的48．21％，年径流量极值比为3．08，径流量呈微弱减小趋势，有利于黄河上游水资源的综合开发利用；③黄河上游径流量存在28、8、5 a的显著周期。
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