Abstract <p>Low-molecular-weight organic acids (LMWOAs) are important organic compounds in Chinese fir (<i>Cunninghamia lanceolata</i> (Lamb.) Hook) litter, but their effects on Chinese fir plantations are unclear. The effects of 0.2, 1, 5, and 25 mmol/L LMWOAs on growth, antioxidant characteristics, and resource distribution of Chinese fir seedlings were studied by simulation experiments with exogenous organic acids (oxalic acid, malonic acid, malic acid, and citric acid). Results showed that the overall effects of LMWOAs on seedling morphology followed the pattern “low is equal promotion, high is inhibition”, and 5 mmol/L had the strongest promoting effect on seedling growth, especially on leaf and root growth. The activities of superoxide dismutase, peroxidase, and catalase increased gradually after treatment with 0.2–5 mmol/L LMWOAs. However, concentrations above 5 mmol/L could cause antioxidant enzyme system disorder. Malondialdehyde content was increased significantly after treatment with 25 mmol/L LMWOAs, indicating that LMWOAs may induce membrane lipid peroxidation in seedlings. Treatment with 0.2–5 mmol/L LMWOAs promoted phosphorus accumulation (mainly in the leaves and roots) and root, stem, and leaf biomass increase; biomass was mostly concentrated aboveground. Overall, the ecological functions of Chinese fir – derived LMWOAs were beneficial to the growth of Chinese fir when applied at appropriate concentrations, whereas higher concentrations induced auto–toxicity.</p>