【Objective】Straw returning is generally considered to be an effective way to increase soil "carbon sink" and mitigate climate change. China is rich in straw resources, but the rate of straw returning to the field is less than 20%, which is the main reason for a long-term deficit of carbon pool in farmland soils in China. There are many kinds of straw resources in subtropical region, which also account for about 30% of the total output of the country. Therefore, clarifying the quantitative relationship between the amount of straw returning and soil carbon sink in subtropical areas of China is an important basis for formulating carbon sequestration measures and implementing national strategies such as carbon neutralization.【Method】Paddy soil in Fujian Province, a typical subtropical region in China, was selected as our study area. The spatial database was constructed by the digitization of 1:50, 000 soil map paper data from 84 counties (cities and districts) in Fujian Province during the second soil census in 1982. The soil attribute database is composed of 15, 833 surface samples from the arable land fertility survey conducted by the Ministry of Agriculture and Rural Areas in 2016. ArcGIS software and the PKB method (Pedological Knowledge-Based Method) connect the spatial data and attribute data in a 1:50 000 soil database. Using the latest established 1:50000 soil database and DNDC (DeNitrification and DeComposition) model widely used in the agricultural ecosystem, the future dynamic changes of soil organic carbon under different rates of straw returned in Fujian Province were simulated. 【Result】 Results showed that the average annual carbon sequestration rates can reach 173, 302, 478 and 838 kg·hm^-2, and the sequestration of carbon amounts were 11.56, 20.15, 31.90 and 55.95 Tg during the period of 2017-2053 under the treatments of conventional management (15%), straw returning of 30%, 50%, and 90%, respectively. Straw was returned to the field from the perspective of carbon sequestration rate, the average annual carbon sequestration rates of Acid sulfate paddy soils and Salinized paddy soils were the highest, which ranged from 220 to 920 kg·ha^-1 under different straw returning rates. In terms of total carbon sequestration, the total carbon sequestration of Percogenic paddy soils and Hydromorphic paddy soils under different straw returning rates accounted for 81% of the total carbon sequestration over the whole province. Considering the administrative areas, the average annual carbon sequestration rate and total amount in Longyan and Quanzhou were relatively large, ranging from 202~937 kg·hm^-2and 1.55~8.34 Tg under different straw returning rates, respectively.【Conclusion】In general, the increase in straw returning ratio contributed significantly to the "carbon sink" of paddy soil in Fujian Province, which is worth promoting. However, under different straw returning rates, due to the influence of soil properties, climate, fertilization and other factors, the contribution of different soil subtypes and administrative regions in Fujian Province to carbon sequestration varies greatly. In the future, it is necessary to formulate reasonable management measures for carbon sequestration and emission reduction for different soil types and prefecture-level cities.