As the essential nutrient elements of plants and the most basic constituent elements of ecosystem, carbon (C), nitrogen (N), and phosphorus (P) play an important role in biogeochemical cycle and maintaining stability of ecosystem structure and function. Under the background of carbon peak and carbon neutralization, in order to accurately evaluate the carbon sequestration and sink increasing function of regional vegetation and scientifically guide vegetation management, we investigated Pinus massoniana secondary forests of 14, 25, 38, 45 and 62 years old in Wuling Mountains Area of Chongqing. Contents and stoichiometry of C, N and P in various organs (leaf, branch, stem, root and bark), litter and soil of P. massoniana forests at five different stand ages were studied. The results showed that C, N and P contents of P. massoniana leaf ranged from 444.48 to 518.03 g/kg, 12.31 to 16.15 g/kg, and 1.75 to 2.21 g/kg, respectively, and overall presented a nutrient pattern of "moderate C, deficient N and sufficient P", and the growth of P. massoniana in this study was mainly limited by N. C, N and P contents in various organs of P. massoniana, as well as their stoichiometry, were differently affected by stand ages and their variations were different, but were significantly affected by organs (P<0.05). C content in bark was the largest, and N and P contents in leaf were the largest in various organs. Litter C, N and P contents of P. massoniana forests, as well as their stoichiometry, were not significantly affected by stand ages (P>0.05). The soil P contents of P. massoniana forests were lower (ranging from 0.09 to 0.41 g/kg), but their stoichiometric ratios of various soil layers were generally higher and differently affected by stand ages. C, N and P contents, as well as their stoichiometry presented the significant correlation between various organs and litter and soil of P. massoniana forests (P<0.05). C and N contents in leaves were significantly positively correlated with soil N content, but P content in leaves was significantly negatively correlated with soil N content. Therefore, for the P. massoniana secondary forests in this region, our findings suggest that appropriate forest management measures such as increasing soil nitrogen fertilizer or replanting nitrogen fixation trees under forest should be taken to enhance the capacity of forest carbon sequestration and sink increasing.