Abstract: Intraspecific competition, as a long-standing and constantly adjusted ecological relationship, is an important factor affecting the variation of population mortality. In order to clarify the effect of intraspecific competition on the population mortality of Pinus massoniana during ecological restoration, three sample plots were set up in Changting County of Fujian Province. The survival status of pioneer species of Pinus massoniana was investigated, and the intensity of intraspecific competition was quantified by using Hegyi competition index. The results showed that in the later period of pioneer stage, the individual size distribution of Pinus massoniana was scattered, and the intensity of intraspecific competition was the most intense. In the middle and early periods of pioneer stage, the variability of individual size of Pinus massoniana was low, and the intensity of intraspecific competition in the early stage was higher than that in the middle stage. With the increase of intraspecific competition intensity, the mortality risk of seedling increased. Intraspecific competition significantly affected the population mortality of Pinus massoniana in the early and middle periods of pioneer stage during ecological restoration, but in the later period of pioneer stage, intraspecific competition was not the main factor affecting the population mortality of Pinus massoniana. The research results showed that the effects of intraspecific competition on the population of Pinus massoniana were different in stages, and the individuals of different sizes in the population had different responses to intraspecific competition.