Abstract: In this study, one hm²(100 m × 100 m)Pinus massoniana and Quercus aliena mixed forest was selected in Baotianman National Nature Reserve as sample plot. All trees in the plot(DBH ≥ 1 cm)were investigated, and intra and inter species competition of P.massoniana was studied by Hegyi competition index model. The results showed that there were many large diameter trees, but less seedlings, and the number of P.massoniana increased gradually with the increase of diameters. There were 1 581 competitive trees, of which were many young trees and the number of competitive trees decreased gradually with the increase of diameters. The total intensity of intraspecific competition about object woods(244.92)was much larger than that of interspecific competition(176.10)and the intensity of intraspecific competition of P.massoniana increased with the increase of DBH, while the intensity of interspecific competition decreased with it. The other competitive trees had competitive pressure on P.massoniana and the sorted relationship was Quercus acutissima>Quercus aliena>Platycarya strobilacea>Quercus variabilis>Picea koraiensis>Cyclobalanopsis myrsinifolia>Quercus aliena var. acutiserrata>Lindera glauca>Ulmus pumila. A function regression was performed to simulate the correlation between diameter and intensity of the competition. It is founded that there was an exponential relationship between them with significant correlation CI=A_e^BD(P < 0.01), this model could be used to predict the community competition of P.massoniana in the plot.