Abstract: Based on field survey and documented data,altitudinal patterns of floristic composition in Mountain Yao Nature Reserve were examined.The results indicated that proportions of temperate elements showed a monotonously increasing trend,while that of tropical elements decreased against altitudinal gradients.The floristic equilibrium point was found at the elevation of 2000 m above sea level.Under the floristic equilibrium point,the majority was of tropical flora,and while above the point,temperate flora was dominant.The cluster analysis based on floristic elements showed that vertical vegetation band was constituted by dry & hot valley vegetation(below 1500 m),Form.Pinus yunnanensis(1500-2000 m),evergreen-broad-leaved forest(2000-2600 m),hard-evergreen broad-leaved forest(2600-3100 m),subalpine shrub(3100-3600 m) and alpine meadow(above 3600 m).