The Grain for Green Project have played an important role in preventing soil erosion and restoring the regional ecological environment in the hilly Loess Plateau region, meanwhile it is important to research biomass and carbon pool of forest ecosystems. There is the close relationship between forest biomass and fixed carbon of forest ecosystems. Robinia pseudoacacia is a typical tree species for the Grain for Green Project in the hilly Loess Plateau region in Gansu Province. The amount of biomass directly affected the function of fixed carbon of Robinia pseudoacacia plantations ecosystems, so the plot investigation and biomass measurement were carried out in the Robinia pseudoacacia plantations afforested in three periods (5 years, 8 years and 11 years) and two slopes(sunny and shady slope). In different plot of Robinia pseudoacacia plantations, we investigated carbon content, carbon storage and allocation of the different tree organs, shrub layers, grass layers, litter layers and soil layers, respectively. The results showed that the average carbon content in different organs of Robinia pseudoacacia ranged from 43.02% to 50.89% and decreased in the order stem > fine-branch > medium-branch > thick-branch > leaf > stump > large-root > thick-root > small-root > medium-root > bark > fine-root. The average carbon content ranged from 35.76% to 42.74%, ranged from 35.83% to 43.64%, ranged from 39.55% to 41.77% in shrub, grass and litter layers, respectively. The average carbon in the soil layer (0-100cm)ranged from 0.22% to 0.99% and increased with conversion years but gradually decreased with the increase of soil depth.Carbon stocks in the different components of the studied forest ecosystems were in an order as: soil > vegetation > litter. Carbon storage on the sunny and shady slope of 5-,8-and 11-year plantations followed as:the ecosystem was 52.52 t/hm², 58.93 t/hm², 73.72 t/hm²and 49.95 t/hm², 61.83 t/hm², 79.03 t/hm². And the soil layer (0-100cm depth) was the largest carbon storage compont, which stored 39.5 t/hm², 42.08 t/hm², 49.68 t/hm²and 35.61 t/hm², 44.31 t/hm², 52.64 t/hm². And the vegetation layer component stored 12.88 t/hm², 17.29 t/hm², 24.69 t/hm²and 14.72 t/hm², 18.10 t/hm², 27.30 t/hm². And the tree layer stored 12.56 t/hm², 16.85 t/hm², 24.04 t/hm²and 14.34 t/hm², 17.52 t/hm², 26.39 t/hm². Of the tree layer, the stem was the highest carbon storage organ. The annual net primary productivity of sunny and shady slope were estimated to be 5.21 t·hm^-2·a^-1 and 6.57 t·hm^-2·a^-1 in the 5 years Robinia pseudoacacia plantation, and annual carbon storage were 2.54 t·hm^-2·a^-1 and 3.10 t·hm^-2·a^-1. Slop aspect and restoration years were the important factors affecting the carbon stock in Robinia pseudoacacia plantations. It was considered that Robinia pseudoacacia had a good carbon sequestration function, being able to be an ideal tree species in the hilly Loess Plateau of Gansu Province. And it may contributed to proper selection of Robinia pseudoacacia forest efficient management of young forest, offering great potential for future carbon sequestration, especially in the hilly Loess Plateau.