Rapid urbanization has resulted in an increase in urban carbon emissions, the degradation of the urban ecosystem, and the escalation of urban environmental issues. It was of utmost importance to define the equilibrium between the supply and demand of urban ecosystem services in light of the rising demand for these services. In karst multi-mountainous urban built-up areas, there were a large number of urban remnant mountains (URMs), which provided a variety of irreplaceable ecosystem services. In order to explore the effect of changes in landscape composition on carbon sequestration services, taking the built-up area of the Guiyang city center as the study area, the spatial-temporal evolution characteristics of the supply and demand of carbon sequestration services and differences in landscape composition within cells were analyzed through the CASA model, multi-source data fusion model, and Arc GIS spatial analysis. Results showed that: (1) From 2010 to 2020, the total carbon sequestration service supply and demand of the Guiyang built-up area showed a decreasing trend; (2) The overall supply and demand space of carbon sequestration services presented a transitional structure of “central city-periphery,” but some supply cells were embedded in the city in a scattered manner; (3) When the percentage of construction land in the cell reached 28.8%, the percentage of evergreen broadleaved forest and evergreen needle-leaved forest would be 30.9% and 4.6%, respectively, and the demand for carbon sequestration services would be generated in the cell. The results of this study could provide guidance for urban planners and policy makers to protect urban ecological security and promote sustainable urban development.