Abstract: In this study, the different stand ages of Pinus massoniana plantation in the hill and mountain site type districts, including 4 site type groups, 6 site type subgroups, and 15 site types, were selected as the research objects to reveal the effects of site type and stand age on the ecological stoichiometry of Pinus massoniana plantation in Sichuan Province. And the needles C, N, and P contents and stoichiometric ratios of Pinus massoniana were analyzed. The results showed that the needles average C, N, P contents of Pinus massoniana in Sichuan Province were 524.34±29.09, 10.28±0.51, and 0.99±0.18 g/kg, respectively; and the needles C∶N, C∶P, and N∶P ratios were 51.08±3.68, 543.90±97.40, and 10.73±2.24, respectively. Across all the plots, the needles C, N, P contents and stoichiometric ratios were significantly（P＜0.05) affected by the site type and the stand age. Within the same stand age, the needles C∶N, C∶P, and N∶P ratios were higher in the hill than in the mountain, and the C content, C∶N ratio, and C∶P ratio were higher in the sandy yellow soil, lower slope of the hill, and the sunny steep（15°-35°) slope in 600-1 000 m altitude of the mountain. The suitable site types for Pinus massoniana in Sichuan Province were the lower part of the hilly sandy yellow soil slope and the 600-1 000 m altitude sunny steep（15°-35°) slope of the mountain sandy yellow soil. In these suitable sites, the needles C storage and the utilization efficiency of needles N and P nutrients were higher than the other sites. Within the same site type, contrary to the change trend of needles N and P content, the needles C content and stoichiometric ratios decreased with the age of forest during the period from the young stand to the near mature stand, while increased with the age of forest during the period from the near mature stand to the mature stand. The Pinus massoniana may have been limited by N before the near mature stand but limited by P after this age of forest.