Biomass-based carbon (C) stock estimation is the most accurate method for estimating the C stock in forestry. To accurately estimate the Manchurian ash (Fraxinus mandshurica Rupr.) C stock, the provenance effect on C traits was evaluated using 20 F. mandshurica provenances planted in 2 test sites in Northeastern China. A total of 360 trees were destructively sampled. The results showed that provenance effects were significant on the concentrations and amounts of C for F. mandshurica, indicating that integrating provenance factors will improve the accuracy in estimating forest C stocks. The growth rate had no significant effect on the C concentration, indicating that using fast-growing provenances for afforestation will sequester the most carbon dioxide. The allocation of C concentration and C amount gradually decreased along apical extensions, indicating that there was a balance between C allocation to storage and allocation to growth for F. mandshurica. The geographic factor analysis showed that both climate at origin and environmental factors at test site could srongly influence C traits. Allometric equations were fitted between the C amount and DBH, and the C amount can be estimated by the equation and the DBH, which is easily measured. In summary, our research results increase the accuracy of estimating the C storage of F. mandsurica, provide a theoretical basis for increasing C sequestration in artificial afforestation using fast-growing provenances.