根据黄河中上游及邻近地区旱涝等级、降水量和树木年轮指数等历史资料及其与天然来水量的关系，建立统计模型，将花园口站天然来水量序列延长至１７４０年。经统计“ｕ”检验，延长序列与原序列有较好的一致性。对２５６年序列的分析结果表明，黄河中上游天然来水量的历史变化具有明显的阶段性和周期性 According to the historical data of drought and flood level, precipitation and tree ring index and its relationship with natural water inflow in the upper and middle reaches of the Yellow River, the statistical model was established to extend the natural water inflow in Huayuankou Station to 1740. The statistical “u” ​​test, the extension of the sequence and the original sequence has better consistency. The analysis of 256-year series shows that the historical changes of natural water inflow in the middle and upper reaches of the Yellow River have obvious phases and periodicities