The accumulation and dynamic stock of soil organic carbon (SOC) in agricultural land are highly sensitive to changes in climate. However, there is uncertainty about how the global SOC cycle will respond to future climate change. In order to assess changes in SOC storage, basing on the historical weather data and field observations (1951–2018), the study used the DeNitrification-DeComposition (DNDC) model to simulate future SOC storage in an arid oasis under three representational concentration paths (RCPs): RCP2.6, low-end path; RCP4.5, middle stable path; and RCP8.5, high-end path) for the period from 2018 to 2086. Farmland soil in the Yanqi Basin in northern China was divided into grid units using ArcGIS, and then kriging interpolation was used to extract the mean value of the 200 grid units to calculate regional changes in SOC storage. The model indicated that more than 92.75 % of the measured results accurately simulated the SOC storage in Yanqi Basin cropland. The measured SOC storage in the Yanqi Basin was 1.32 Tg C in 2018. The range of SOC density was 653.27–5527.04 kg C/hm² under the historical climate scenario, and 1863.99–4581.16 kg C/hm², 2372.74–6910.15 kg C/hm², and 623.656–5431.95 kg C/hm² under the RCP 2.6, RCP 4.5, and RCP 8.5 scenarios, respectively. The simulation results show that, compared with the SOC stock in 2018, the SOC stocks in the oasis area in the future will show a rapid decline under the historical climate scenario (7.6 % decrease) as well as in the RCP 2.6 (3% decrease), RCP 4.5 (9.17 % decrease), and RCP 8.5 (16 % decrease) scenarios. These results indicate that organic carbon outputs and density will decrease faster under high emissions and more slowly under low emissions. This study provides supporting data and a scientific basis for increasing soil organic carbon in cropland and for the management of oasis soil to mitigate the effects of future climate change.