The Danjiangkou Reservoir is an important water source for the South-to-North Water Diversion Middle Route Project. Exploring changes in the landscape pattern and nitrogen and phosphorus removal capabilities of the reservoir area provides a scientific basis for future landscape planning and ecosystem function enhancement. Taking Danjiangkou City as the research area, using the landscape pattern index and the InVEST model to study the landscape pattern and nitrogen and phosphorus removal capacity of the reservoir area from 2003 to 2018. Pearson correlation analysis and RDA analysis were used to analyze the relationship between them and analyze the factors causing the change of nitrogen and phosphorus removal capacity. The results show that in terms of patch types, the water area and woodland continue to increase, the area of cropland and orangery land gradually decreases, and the area of urbanized land shows an overall growth trend. At the landscape level, the landscape shape index continues to decrease, the contagion index and the aggregation index indicate an overall increasing trend, the shape complexity decreases, the landscape agglomeration degree increases, the interspersion and juxtaposition index increases by 5.58, and the Shannon diversity index has a smaller change. Each patch type tends to be regular, showing a balanced trend distribution. In 2003, 2008, 2013 and 2018, the nitrogen and phosphorus removal capacity continued to increase. The total output of TN was 899.224 t, 801.481 t, 776.979 t, and 672.149 t, respectively, and the total output of TP was 77.308 t and 69.921 t, 68.163 t, 60.802 t, respectively. The water removal capacity of TN and TP has increased by 25.3% and 21.4% respectively in 15 years. The classification of the importance of nitrogen and phosphorus removal capacity shows that extremely important and highly important areas are mainly distributed in reservoir areas, river banks and woodland areas. Pearson correlation analysis and RDA analysis show that the woodland area and the output of nitrogen and phosphorus are significantly negatively correlated on the patch type, while the output of cropland land, orangery land, and urbanized land is positively correlated with the output of nitrogen and phosphorus. At the landscape level, there is a significantly positive correlation between the output of nitrogen and phosphorus and the landscape shape index, and a significantly negative correlation between the interspersion and juxtaposition index, and the negative correlation with the contagion index and the aggregation index. Therefore, plants that removing nitrogen and phosphorus can be planted in areas with high nitrogen and phosphorus output in the reservoir area. A series of measures, such as adjusting landscape structure, rationally planning land use, increasing forestland area, constructing riparian vegetation buffer zone to fully slow down runoff, can fully guarantee the water quality safety of reservoir area.