Abstract: The morphological characteristics of 10 Pinus yunnanensis.population needles,sampled from the south-east,mid-part and north-west of Yunnan plateau,were extensively investigated,observed and analyzed according to the principle and method of ecology and comparetive morphology.The morphological diversity and ecological adaptation were analyzed combined with the meteorological factors.The morphological characteristics of P.yunnanensis.needles presented polymorphism from south-east,mid-part to north-west of Yunnan plateau.With the altitude(sampled stripe) increasing,the general trend of the morphological variance presented the tendency of miniaturization:the length of needles,frequency of the 3 needles per bundle,needle number per bundle.The length of the needle presented "preponderant needles,growing faster".The long term adaptation and evolution molded the relatively steady of the morphology and structure.The diversity of morphology was obvious as a result of the ecological adaptation under the complicated geographical and ecological environment.