[Background] The soil organic carbon storage and its temporal and spatial variation in forest ecosystem are not only of significance for global carbon cycle and carbon balance study, but also the crucial for developing sustainable forest management measures. To comprehensively understand the characteristics of soil organic carbon ( SOC) and accurately assess the soil carbon stock of the plantations, and therefore, provide evidence for plantation management in this region, This study was carried on the Pinus tabuliformis and Acer truncatum plantations of different stand density in rocky mountainous area of northern China. [Methods] We examined the SOC content, SOC density and SOC storage and their vertical distribution between 0 -100 cm soil depth of P. tabuliformis and A. truncatum two plantations with different stand densities in the rocky mountainous region of northern China and also discussed the correlations of SOC content and soil physicochemical properties, i. e. , soil density, pH,total nitrogen, and available potassium. [Results] The results showed that the average SOC content and SOC density of A. truncatum plantations were both higher than these of P. tabuliformis plantations, indicating that under the similar climate and soil condition, the soil of A. truncatum plantations had greater carbon sequestration than the P. tabuliformis plantations. Meanwhile, the quantity of humus and plant roots in soil layers decreased with the increase of soil depth, both the SOC content and SOC density in 0 -10 cm layer were the highest among the 0 -100 cm soil depth and decreased with the increase of soil depth. The SOC content of the A. truncatum plantations showed no difference between the high and low stand densities, while the SOC density of the A. truncatum plantations in high density was greater than lower ones. However, both of the SOC content and SOC density of the P. tabuliformis plantations in the middle density was much higher than that in the high and low density ones. Specifically, the SOC density was the highest, when the stand density was 1 700 and 2 350 stems per hm2 for the P. tabuliformis plantations and the A. truncatum plantations, respectively. The SOC content of the P. tabuliformis and A. truncatum plantations showed significant negative correlation with soil density, while highly positive correlation with the total nitrogen and available potassium. Nevertheless, only the SOC content of the P. tabuliformis plantations was affected by soil pH value. [Conclusions] In this study the SOC content had the most significant relation with the soil total nitrogen among all the measured soil physicochemical properties in both of the P. tabuliformis and A. truncatum plantations. In summary, the A. truncatum plantations had greater potential for carbon sequestration than the P. tabuliformis plantations in rocky mountainous area of northern China, both SOC content and SOC density were greatly influenced by tree species and stand density.