Abstract: This paper analyzed the niche breadth and niche overlap of dominant species of forest community in Xiaowutai Mountain, and fitted the response patterns of dominant species to the environment gradients by generalized additive models. The results showed that a total of 392 species of vascular plants, belonging to 222 genera, 75 families were recorded in 148 quadrats. A total of 36 dominant species were selected from the tree layer, shrub layer and herb layer by importance va-lues. Betula albosinensis, Betula platyphylla, Larix principis-rupprechtii, Pinus tabuliformis at the tree layer, Spiraea pubescens, Abelia biflora, Rosa bella, Corylus mandshurica at the shrub layer, Carex breviculmis, Deyeuxia arundinacea, Sanguisorba officinalis, Carex siderosticta at the herb la-yer had higher niche breadth, and these species had greater competitiveness and stronger environmental adaptability. In the same layer, niche overlap index was high indicating that species had similar habitats, and there was competitive relationship between them. Although Acer momo and Quercus wutaishanica had high niche overlap, their competition was not strong in the condition of rich resources. There was niche overlap between B. platyphylla and a variety of mixed tree species including A. momo, Q. wutaishanica, Sorbus alnifolia, and limited resources leaded to strong competition in these communities. The adaptability of each species to environmental factors was diffe-rent. The response of most dominant species to altitude showed a single peak curve, and they distri-buted within a certain altitude range. The response of some dominant species to altitude was linearly increased or decreased, and concentrated at high altitudes or low altitudes. The response of dominant species to slope position was similar to altitude. The dominant species showed a linear change along the slope, showed significantly positive correlation with soil temperature, and showed the cha-racteristics of shade-requiring or sunny-requiring. The response of B. albosinensis, A. biflora, H. bretschneideri, C. breviculmis, C. dahurica to litter layer thickness and soil thickness showed linearly increased. The response of L. principis-rupprechtii, B. albosinensis, P. fruticosa, D. arundinacea to soil moisture showed linearly increased, while linearly decreased to soil electrical conductivity. Most dominant species to soil pH and environmental disturbance showed a single peak curve, and the others showed linearly decreased.