As the natural boundary between the eastern Yunnan plateau and the southwestern Yunnan in Hengduan Mountains, the large-scale prominent terrain leads to obvious regional difference of climate and vegetation on both sides of Ailao Mountain. In this article, a comparative analysis is made on plant species floristic elements of sediment spore-pollen in two sample plots beside the main peak respectively. The results show that there is a remarkable difference on sediment spore-pollens between these two sample spots while there is no on the topsoil spore-pollens. The tropical genera elements of sediment spore-pollens is higher in the western sample plot (6.8%) than one in eastern part (4.7%) because the western plot is controlled by India summer monsoon at all times. And the north temperate elements of sediment spore-pollens is lower in the western sample plot (13.4%) than one in eastern part (26.4%) because the eastern plot is influenced evidently sometimes by East Asia winter monsoon. In a word, Ailao Mountain is one of important boundaries between India summer monsoon and East Asia winter monsoon.