We made an investigation on the Ormosia saxatilis in the Ormosia saxatilis community in the natural forest of Guizhou, studying the niche breadth values, niche proportional similarity values and niche overlapping values of the major tree species at different levels through the method of quantitative analysis. The results are as follows. 1) There is a large difference in the niche breadth of the tree layers of Ormosia saxatilis, Carpinus pubescens, Celtis sinensis, Cyclobalanopsis glauca etc, measured with Levins and Shannon-Wiener indexes, but the sequences of the first ones are basically the same. 2) In the arborous layers, the trees have a large niche breadth. Their B_(SW)i and B_(H)i are as following: 0.6559, 0.5113, 0.3635, 0.3369 and 0.9086, 0.4545, 0.4071, 0.3298. 3) In the shrub layers, O. saxatilis, Platycarya longipes and other species have large niche breadth as well. 4) The niche breadth can reflect the species' adaptive norm, that is to say, the larger the niche breadth is, the stronger the species is. 5) The niche breadth and the niche overlap are closely linked. Generally speaking, species with a larger niche breadth own larger overlap values. Besides, the species and other species have more similarities and larger overlap values. In a word, the larger overlap values they have, the more similarities they have in utilizing resources, and the more intense the competiveness will become.