Understanding the evolution of the relationship between urbanization and ecosystem services is crucial for establishing an ecological security paradigm, optimizing resource allocation, and achieving regional sustainable development. In this study, Jiangxi Province was taken as an example, and the land use/cover change (LUCC) in 2035 and its effects on ecosystem services were investigated. We first employed the LUSD model to simulate LUCC in 2035 by coupling macro driving factors and micro parcel dynamics. Then, the InVEST model was used to estimate four key ecosystem service functions (water yield, sediment delivery ratio, carbon storage, and habitat quality) and characterize their spatiotemporal patterns to reveal the future response. The results showed that: (1) Compared to 2020, the demand for construction land in Jiangxi Province in 2035 would continue to increase with population and socio-economic fluctuations, leading a further reduction in forestland and arable land. (2) Urbanization showed a positive correlation with water yield and sediment delivery ratio and a significant negative correlation with carbon storage and habitat quality. With increasing of urbanization indicators, water yield and sediment delivery ratio would increase, while carbon storage and habitat quality would decline in 2035. Spatially, water yield decreased from north to south, while sediment delivery ratio, carbon storage, and habitat quality all showed a distribution pattern of low in the middle and high around the periphery. (3) Relative to 2020, both trade-off and synergistic correlations intensified in Jiangxi Province in 2035. The synergistic correlation accounted for approximately 83%, dominating. This study evaluated the future ecosystem service functions in Jiangxi Province, analyzed their trade-off and synergistic relationships, and explored to disclose the response relationship between urbanization and ecosystem services. These findings provided a scientific basis for balancing urban development and ecological protection, and for formulating relevant policies.