Ecosystem services (ESs) have a non-negligible contribution to Sustainable Development Goals (SDGs) realization. However, the complex trade-offs between the SDGs undermine the contribution. The contribution of ESs to the multiple SDGs co-realization needs to be further explored. Taking a typical ecologically fragile basin in the Loess Plateau as an example, this study combined the ESs supply and demand with the expert knowledge method to estimate the changes of SDG1,2,6,15 scores from 1990 to 2020. Network analysis was introduced to construct the SDGs network, integrating degree centrality and closeness centrality to identify SDGs of high importance in the network. The potential changes of SDGs networks in 2050 were simulated under different shared socioeconomic pathways and representative concentration pathways (SSPs-RCPs) scenarios. The results showed that the deficit risk of water yield and carbon sequestration increased. The four SDGs scores mainly showed a trend of decreasing and then increasing, with SDG6 showing the most drastic change. The synergies among changes in the four SDGs scores gradually strengthened in the northern basin. The proportion of sub-basins with SDG2,6 as the highest Node Importance increased from 18.75% and 0% to 26.67% and 40.00%, respectively. The role of SDG2,6 on the synergies among changes in SDGs scores strengthened. The four SDGs scores generally decreased under the different scenarios, with a particularly significant decrease in SDG15. The SSP1-RCP2.6 scenario had the least decrease in the four SDGs scores. The role of SDG15 on the synergies among changes in SDGs scores was strongest under most scenarios. The proportion of sub-basins with SDG15 as the highest Node Importance accounted for more than 58% under SSP1-RCP2.6 and SSP5-RCP8.5 scenarios. By integrating ESs supply and demand into SDGs network analysis, this study attempted to construct a toolkit for integrating ESs into SDGs co-realization.