[Objective] To investigate the spatiotemporal evolution patterns and driving effects of net carbon sink in Ningxia’s farmland ecosystems under the "dual carbon" goals. [Methods] Taking the region’s farmland ecosystem as the research object and based on the carbon emission factor method released by the Intergovernmental Panel on Climate Change（IPCC）, a calculation system for net carbon sink in farmland was established by measuring the difference between carbon absorption during the crop growth period and carbon emissions from agricultural production activities. The net carbon sink volume and net carbon sink intensity in Ningxia from 2003 to 2022 were calculated. ArcGIS visualization, center of gravity shift model, and the standard deviation ellipse were employed to characterize the spatiotemporal characteristics of net carbon sink in farmland. Furthermore, the Logarithmic Mean Divisia Index（LMDI） model was applied to identify the main driving factors of net carbon sink in Ningxia’s farmland. [Results] 1) In terms of temporal characteristics, total net carbon sink in Ningxia’s farmland showed an overall increase during the study period, increasing from 3.38×10⁶ t in 2003 to 7.56×10⁶ t in 2022. Additionally, the net carbon sink intensity exhibited a rising trend, rising from 2.55 t/hm² in 2003 to 6.35 t/hm² in 2022. 2) For spatial characteristics, the distribution of net carbon sink in Ningxia’s farmland across counties shifted from a pattern of "higher in the northwest and lower in the southeast" to "higher in the north and lower in the south". The center of gravity of net carbon sink in farmland moved from Lingwu City in Yinchuan to Hongsibao district in Wuzhong, with a shift distance of 40.15 km. 3) In terms of net carbon sink sources, chemical fertilizer application was the primary source of carbon emissions in Ningxia’s farmland ecosystem, accounting for 36.06% of the total. Corn was the main contributor to carbon absorption, representing 50.90% of total carbon absorption. 4) Net carbon sink efficiency in farmland and agricultural labor were negative driving factors for net carbon sink in Ningxia’s farmland, whereas economic development level, urbanization level, and agricultural industrial structure were positive driving factors. [Conclusion] Farmland ecosystems in Ningxia exhibit significant spatiotemporal differentiation in net carbon sink, with the carbon sink effect strengthening over time. Optimizing both agricultural industrial structure and crop planting structure can effectively strengthen carbon sink capacity of farmland. This study provides theoretical support for ecological carbon sink management in arid regions, offering strategic guidance for developing carbon emission reduction policies and achieving "dual carbon" goals in northwest China.