Castanopsis kawakamii is a rare species recorded as second grade of protected plant in China. A natural community of C. kawakamii forest with an area of 700 hm^2 at Shanmin in Fujian Province is considered to be the largest and unique C. kawakamii forest in China. According to data obtained from field investigation, the intraspecific and interspecific competitions of C. kawakamii in six communities were analyzed quantitatively by using Hegyi's competition index model for individual tree. Intraspecific competition intensity in this species reduced with the increase of diameter class of the trees. The competition intensity among each pair of species was in the order Pinus massoniana-Castanopsis kawakamii>C. kawakamii-C. kawakamii>Schima superba-C. kawakamii>Elaeocarpus decipiens-C. kawakamii>Litsea mollifolia-C. kawakamii>Symplocos stellaris-C. kawakamii. A remarkable regression model of the relationship between competition intensity and diameter class of objective tree individuals is established. The model can be applied to predict the competition intensity in forest of C. kawakamii.