Abstract: Principles of vegetation ecology and method of multivariate analysis(Double Sieving Step Regression)are applied to reveal the general relationship between forest vegetation and its habitats in the upper and mid-dle reaches of Xunhe River basin and their adjacent areas. The results show that the species diversity and richness of synusia have higher significance for indicating the correlation between forest community and habitats.Two primary conclusions are deduced from the results：(1)the dominant habitat factor guiding forest distribution and growth is elevation and (2)soil pH is also an important factor in affecting species growth of many communities.

Key words: “scatter degree&rdquo, method, comprehensive evaluation, river ecosystem health.