In order to provide data support for policy formulation and measures implementation of natural forest protection in China, the dynamics of carbon storage and carbon sink (source) characteristics of forest vegetation in the natural forest protection project (NFPP) region were estimated and evaluated in the last 20 years. Based on data from 6-9th Chinese National Forest Inventory (CNFI) of the NFPP region, the forest vegetation was divided into arbor forest, shrubbery, bamboo, open forest, scatted trees, and "four-side" trees. By means of tree biomass model and related parameters to carbon accounting from forestry industry standard and biomass conversion and expansion factor from the weighed biomass average method, total carbon storage of forest vegetation were estimated in the NFPP region and provincial level. The carbon storage and carbon density of the arbor forest were evaluated by origins, age groups, and dominant tree species (groups). The changes of total carbon storage of forest vegetation and carbon storage of arbor forest with time were quantified to clarify carbon sink (source) characteristics. The results showed that the total carbon storage of forest vegetation in the NFPP region in 6-9th CNFI was 2999 TgC, 3254 TgC, 3585 TgC, 4097 TgC, respectively, with average annual growth rates of 1.65%, 1.96%, and 2.70%. Carbon storage was concentrated in the regions of northeast and southwest of China, and Sichuan province had the highest carbon storage which accounted for more than 20% of the total amount of NFPP region in 6-9th CNFI. The arbor forest carbon storage was the main body of the forest carbon storage, which accounted for more than 80% of the total forest carbon storage in every inventory with little variation in the proportion. Further, the proportion of natural forest carbon storage in arbor forest decreased from 94.67% to 90.28%. The proportion of plantation forest was gradually increasing, but the carbon density was lower than half of natural forest in the 9th CNFI. Among different age groups, the middle-aged forest had the highest carbon storage, and near-mature forest had the fastest growth rate in carbon storage. The carbon density gradually increased from young-aged forest to over-mature forest and the tendency was the same in 4 periods. Pure forest carbon storage accounted for more than 60% that of arbor forest, and the carbon storage and carbon density of most tree species (groups) increased over time. In the 7-9th CNFI, the total carbon sequestration of forest vegetation in the NFPP region (current period relative to the previous period) were 255.33 TgC, 331.46 TgC, and 511.53 TgC, respectively. They contributed to the total forest carbon sink in China from 53.78% in the 8th CNFI to 67.46% in the 9th CNFI. In particular, arbor forest contributed 68.71% to the national arbor forest carbon sinks while natural forest in the NFPP region contributed 75.90% to arbor forest carbon sinks in the NFPP region. The arbor forest carbon sinks of each age group had relatively great variation with different CNFIs. The proportion of carbon sinks in young-aged forest and middle-aged forest increased significantly while near-mature forest and over-mature forest decreased. The order of carbon sinks in each age group in the 9th CNFI was middle-aged forest > near-mature forest > young-aged forest > mature forest > over-mature forest. The carbon sink (source) performance of every dominant tree species were different in different CNFIs. In general, the mixed forest had the largest proportion of carbon sinks. In the 9th CNFI, the contribution of mixed broad-leaf forest and mixed conifer-broadleaf forest to the carbon sink of arbor forest were 62.59% and 17.23%, respectively. In pure forest, cypress contributed the most to carbon sink, accounting for 5.43%. The total carbon storage of forest vegetation in the NFPP region had steadily increased over time. Arbor forest was the main body of total carbon storage and natural forest was the main source of carbon sinks. The natural forest protection enhances the carbon sink function of natural forest in China, and promotes the carbon sink function of plantation. The carbon sinks in the NFPP region will have great potential in the future.