Sea level rise (SLR) has a significant impact on the ecosystem services in coastal wetlands. Taking the Liaohe Delta as an example, the SLAMM (Sea Level Rise Affecting Marsh Model) was used to simulate the medium-term (2010–2050) and the long-term (2010–2100) of the spatiotemporal changes of land use in the four scenarios (0.5, 1, 1.5, and 2 m) of sea-level rise by 2100 and then based on the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs Model) to assess and compare the impact of SLR on ecosystem services. The results are as follows. (1) The difference in SLR height greatly influences the transformation of the coastal wetland pattern. In 2100, the core construction land would be affected on a large scale for landward salt marsh migration for 1.5 and 2 m SLR scenarios. (2) Due to inundation, erosion, and vegetation succession, the mean total carbon storage for the four scenarios will decrease by about 0.58 × 106 t. The habitat quality is relatively stable, and its value is about 0.7. The nitrogen and phosphorus loads will be reduced by 26.27% and 28.22%, respectively. The region spatial distribution of freshwater marshes will shrink, while the transformation of salt marshes is inconsistent. The large-scale formation of regularly flooded marshes can also provide high levels of ecosystem services as salt marshes. In conclusion, the coastal wetlands show two evolution patterns under the four sea-level rise scenarios, the two low ones show a slow change, and the two high ones are large. Quantitative assessment of the effects, scope, and intensity of the impact of SLR on the function of ecosystem services in the coastal wetlands can provide reference and indicative significance for wetland development, construction, ecological conservation, and restoration in similar coastal areas under the impact of climate change.