The mountain-river-forest-cropland-lake-grassland system project (hereafter referred to as the (“shanshui project”) is an important ecological project aimed at enhancing ecosystem service functions and promoting the sustainable and virtuous utilization of ecosystems in China. However, systematic evidence remains sparse regarding the impact of the shanshui project on the enhancement of ecosystem service value (ESV). Taking Ganzhou City in Jiangxi Province, the first pilot area of the national shanshui project, as an example and based on seven periods of China Land Cover Dataset spanning from 2010 to 2022, we analyze the spatial-temporal changes in ESV and its trade-off synergistic relationships before and after the implementation of the shanshui project and further explore the contributions of different land use type transformations to the spatial-temporal evolution of ESV. The methods used include the equivalent factor approach, correlation coefficients analysis, geographically weighted regressions, and so on. The results show that: (1) The implementation of the shanshui project effectively reverses the deterioration trend of ESV in Ganzhou city. Specifically, the ESV in Ganzhou city decreased by 4.772 billion yuan in the 13 years, but ESV declined by 480 million yuan less after the project than before it was implemented. This reduction effect is mainly due to the project’s impact in reducing the loss of forest and grassland areas. However, the ongoing expansion of cultivated and construction land and watershed degradation continue to impede the enhancement of ESV in Ganzhou city. (2) The impact of the shanshui project on ESV varies across different regions. Specifically, due to the influence of the shanshui project, the ESV of Gan Dong and Gan Nan, which were regions with low ESV before the implementation of the project, changed from decline to increase, but the ESV of Gan Xi and Gan Zhong, which were regions with medium ESV before the implementation of the project, showed a slight decline. (3) Synergistic relationships are the main relationships of each ecosystem service in Ganzhou city, and the implementation of the shanshui project enhanced the synergistic relationships between most individual ecosystem services, especially between hydrological regulation, raw material production, and other services. However, the synergy relationship between water supply and other services has weakened due to inadequate watershed protection by the project. The study quantified the performance of the shanshui project from the perspective of ESV, which provides a scientific basis to optimize the implementation plan of the shanshui project and helps to improve the scientific and spatial relevance of the follow-up work of the shanshui project.