The impact of regional land use type change on soil organic carbon storage is the core issue affecting the evaluation of ecological environmental effects. According to soil samples and land use data, the effects of land use change of cultivated land on soil organic carbon density (SOCD) and carbon storage (SOCS) in the surface layer (0-20 cm) of the Loess Plateau, Shaanxi, over the past 30 years was studied. The results showed that:(1)The land use conversion rates of cultivated land from 1985 to 2006 and 2006 to 2015 were 2.81% and 17.89%, respectively, indicating that the policy on converting farmlands to forests accelerated the speed of land conversion of land use types in the study area. (2)The changes in surface SOCD of cultivated land over the past three decades in the study area were quite different. The SOCD was 1.73 kg/m² in 1985, and this increased by 8.09% in 2006 and 36.36% in 2015. (3)From 1985 to 2006, the areas of cultivated land remained unchanged and changed were respectively 9429.87 km² and 272.41 km²; the increased SOCS were 927.93×10⁶ kg and 33.8×10⁶ kg, respectively. From 2006 to 2015, the areas of cultivated land remained unchanged and changed were respectively 8119.04 km² and 1768.47 km²; the increased SOCS were 3132.79×10⁶ and 1198.99×10⁶ kg, respectively. ⑷The conversion of cultivated land to forest and other land types supports the increase of top SOCS, and creation of carbon sinks. Therefore, returning farmlands to forests by the tableland of the Loess Plateau in the Shaanxi Province may increase carbon fixation in ecosystems.