The Yellow River headwater basin located in the northeast Tibetan Plateau is the source of the Yellow River. This basin is very sensitive to the change of environment and climate. In this paper, the authors analyzed the pollen in the fluvial and lacustrine fades sediments in the Yellow River headwater basin. The pollen assemblage includes herbaceous pollen (Asteraceae, Artemisia families, Chenopodiaceae, Gramineae) and woody pollen (pine, birch). An analysis of characteristics of various kinds of plant pollen revealed the evolution and change of the palaeovegetation and palaeoclimate in Yellow River headwater basin since the Early Pliocene. The evolution has gone through four stages: the first phase from 2239 ka BP to 901 ka BP was a forest-steppe environment, reflecting a warm and humid climate; the second phase from 901 ka BP to 350 ka BP was a shrub steppe environment, suggesting a cold and dry climate; the third stage from 350 ka BP to 28 ka BP was a grass savanna-meadow grassland environment, implying a cold- humid climate; the fourth stage from 28 ka BP to 8 ka BP was a desert steppe environment, indicating a cold and dry climate.%黄河源盆地位于青藏高原东北部,是黄河的源头地区,对环境和气候变化非常敏感.对黄河源盆地中的河湖相沉积物进行了孢粉分析,获得丰富的孢粉数据,结果显示孢粉组合以菊科、蒿科、藜科、禾本科、松、桦等草本和木本植物花粉为主.通过对各类植物的孢粉组合特征分析,揭示了黄河源地区早更新世以来古植被、古气候的演替和变化.其演变经历了4个阶段:第一阶段223.9～90.1万年,为森林草原环境,反映了温暖潮湿的气候；第二阶段90.1～35万年,为灌丛草原环境,反映了总体干冷的气候；第三阶段35～2.8万年,为稀树草甸草原环境,属湿润寒冷的气候；第四阶段2.8～0.8万年,为荒漠草原环境,反应干冷的气候.
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