Abstract: Land use/cover change (LUCC) is an important cause of carbon storage change in terrestrial ecosystems. Land use change is often constrained by policy, which affects carbon stock changes. To forecast the LUCC of Xi’an in 2030 under the guidance of the policy, and analyze its impact on carbon storage is of great significance for Xi’an policy-making, land use structure adjustment, and the realization of the “double carbon” goal. Based on the land use data (LULC) of 2000, 2010, and 2020, this study selected 11 driving factors and established three development scenarios of business as usual (Q1), ecological protection (Q2), and town development (Q3), respectively, according to the Xi’an “14th Five-Year Plan” policy planning. The PLUS model was used to predict and analyze the spatial distribution pattern of land use in Xi’an in 2030, and the InVEST model was coupled to evaluate the carbon storage of Xi’an in different development scenarios and analyze the change in carbon storage. The results show that: 1) the PLUS model has strong applicability in Xi’an City. The overall accuracy of the model was 0.93 and the Kappa coefficient was 0.89. 2) From 2000 to 2020, the areas of construction lands, grasslands and water bodies in Xi’an increased, while the areas of arable land, woodland, and wetland decreased. From the perspective of the transfer direction, arable land was mainly converted to construction land. 3) Q1 continued with the previous development pattern. In 2030, the quantity of ecological land, such as woodlands and water bodies, under Q2 increased compared with that in 2020, and the construction land areas under Q3 increased by 10.42%. 4) LUCC was the main reason for changes in ecosystem carbon storage. The total carbon storage under Q1 in 2030 decreased by 373.28 t compared with that in 2020, indicating that a continuation of the previous development mode would reduce the total carbon storage. Under Q2 in 2030, carbon storage increased by 564.73 t from 2020, which explains certain ecological protection measures to protect forest land, wetland, and increase the amount of cultivated land. This would also limit the transfer of ecological lands with high carbon density, such as cultivated land, into low carbon density land for construction purposes, potentially slowing the increasing trend of carbon reserves in terrestrial ecosystems. Under Q3, with the acceleration of urbanization, the scale of construction land has expanded, and a large number of urban areas occupy ecological and cultivated lands, which greatly reduces carbon storage. The results show that the major reason for the loss of carbon storage is the large expansion of construction land and the encroachment of ecological and arable land. The implementation of scientific and reasonable ecological protection measures can solve the carbon storage decline problem caused by economic development.