In the context of global warming, quantifying the impact of regional land-use changes on the terrestrial carbon exchange is essential for enhancing ecosystem carbon sequestration and achieving carbon neutrality goals. The Chang-Zhu-Tan (CZT) region, as the economic, cultural, and ecological core of Hunan Province, has undergone significant changes in land use and vegetation structure over the past few decades, deeply influencing the carbon balance of its terrestrial ecosystem. This study employed climate forcing data with a spatial resolution of 1km, CO2 concentration data, and land-use data with a spatial resolution of 30m, in combination with the LPJ-GUESS model, to simulate the spatiotemporal patterns of net ecosystem exchange (NEE), an indicator of terrestrial carbon balance, in the CZT region from 1980 to 2023 under different driving conditions. The individual contributions of climate and land use change to the NEE in the region were further analyzed. The results showed that: (1) Over the past 40 years, rapid urbanization in the CZT region has led to a substantial reduction in cropland and forest land, becoming the key driver of carbon loss in the ecosystem; (2) The NEE for the region has increased at an annual rate of 44.44 GgC/a, indicating net terrestrial carbon emissions, with 98.06% of the region showing an increasing trend in NEE; (3) Land-use changes have contributed to a NEE increase of 7.17 GgC/a, with a total carbon emission of 5293.20 GgC over the past 40 years, of which the expansion of built-up areas accounted for approximately 37.14%; (4) Climate change has contributed 89.75% to the variation in NEE, dominating approximately 93.22% of the region, while land-use changes accounted for 10.25% of the variation, dominating about 6.78% of the region. These findings provide a scientific foundation for optimizing regional land use management and formulating effective carbon neutrality strategies.