Abstract: Land use can cause carbon stock changes by affecting the structural layouts and functions of terrestrial ecosystems. Therefore, research on the relationship between land use changes and carbon stock is greatly significant for optimizing regional land use patterns and making sensible ecological decisions. This study predicted the spatial-temporal changing characteristics of land use and carbon stock in Xi’an under different scenarios in the future using the PLUS and InVEST models and investigated the impact of land use changes on carbon stock. The results are as follows. From 2000 to 2015, the expansion of construction land and the transfer of high-carbon-density land reduced the carbon stock of Xi’an by 2.49×106 t. From 2015 to 2030 the carbon stock continuously declined by 2.14×106 t in the natural growth scenario, and the carbon stock of Xi’an will increase by 6.92×105 t in the ecological protection scenario due to the measures taken for land protection and transfer control. In the cultivated land protection scenario, the cultivated land will be protected, but the high-carbon-density land such as woodland and grassland will be affected by the expansion of construction land during 2015—2030, reducing the carbon stock to 1.60×108 t. As indicated by the analysis of carbon density change, ecological protection measures can increase the changing rate of carbon density. Compared with the natural growth scenario, the ecological protection scenario will increase the proportion of areas with increased carbon density (mainly high-increase areas) from 0.05% to 1.57%. By contrast, under the cultivated land protection scenario, the carbon density will decrease, and high-increase areas will be transformed into moderately-high-increase areas. Based on cultivated land protection, it is necessary to take proper ecological protection measures in the future land use planning of Xi’an to control the rapid expansion of construction land from cultivated and forest land. Optimizing land use patterns can effectively reduce the loss of carbon stock, improve the level of regional carbon stock, and achieve regional sustainable development.