Based on the panel data of Guangxi from 2005 to 2017, the spatiotemporal characteristics and determinants of urban carbon emissions in Guangxi were analyzed using the extended STIRPAT model and the Geographically and Temporally Weighted Regression (GTWR) model. The main findings of our research can be summarized as follows. While the total carbon emissions of cities in Guangxi consistently increased from 2005 to 2014, the growth trend slowed after 2014, leading to a stabilization in the total emissions. In addition, there are significant differences in the total carbon emissions among the cities. The central and northeastern regions have higher emissions, while the southwestern region has lower emissions. Finally, there are variations in the degrees and directions of the impacts that factors have on carbon emissions among the different time periods and cities. Urban land use is a key factor driving carbon emissions, and it has a negative impact on most cities in Guangxi. Meanwhile, factors such as industrial structure, population urbanization, population concentration, and economic growth have significant positive effects on carbon emissions in Guangxi. The influence of urban roads on carbon emissions is generally positive, while the degree of openness to the outside world and environmental regulations has relatively weaker impacts on emissions. In summary, in order to promote the low-carbon transition of Guangxi and achieve high-quality development, the cities in Guangxi should implement differentiated urban carbon reduction strategies that are focused on optimizing urban land use and industrial structure.