Leaves exhibit great phenotypic plastic in both morphology and anatomic structure,and are the most sensitive organ to environmental changes.In this study,leaves of Polygonum paleaceum living at nine altitudes ranged from 3 000 to 4 600 m in Yulong Mountains were sampled.Then the morphological and anatomical structures of these leaves were studied by the paraffin section method and microscopic techniques.The aim is to reveal the adaptive strategy of this plant to different altitudes.The results showed:(1)length,width,and ratio of length to width all decrease with rising altitude,the maximum decrease rates are 84.64%,74.87% and 37.50%,respectively.(2)The leaves of this plant are bifacial,including epidermis,mesophyll and vein.The epidermis is single layer and has thicker cuticle;the palisade of mesophyll is composed by two to three layers of cells.The veins compose some vascular bundles which arrange by a discrete circle.(3)The thickness of the leaves,palisade tissue thickness,spongy tissue thickness and thickness of main vein,length of vascular bundles,and width of vascular bundles all increase with rising altitudes,the maximum increase are 38.32%,47.30%,47.39%,56.46%,173% and 337%,respectively.While the upper and lower epidermis,cell tense ratio,leaf loose degree,ratio of palisade to spongy tissue and number of vascular bundles did not correlate with altitudes significantly.In summary,this study showed the morphological and anatomical structures of P.paleaceum leaves would be changing with increasing altitudes,which would be good for plants to decrease transpiration,increase water conservation and photosynthesis ability.