The transformative period of reshaping China’s Protected Area System (CPAs) requires nature reserves (NRs) to pay greater attention to policy-driven changes in land use as well as ecosystem. We take Anhui Shengjin Lake National Nature Reserve (SJLNNR) as a case study to examine policy-driven changes in ecosystem services and their trade-offs. We find that (1) policy implementation significantly increased the area of wetlands and forests while decreasing the area of cropland and impervious land. Ideally, the area of wetlands and forests could be increased by ~10200 hm². (2) Habitat quality (HQ) and water conservation (WC) are enhanced, with the highest enhancement of 13.09% and 28.18%, respectively. Carbon storage (CS) and food production (FP) showed opposite trends across scenarios. (3) CS demonstrates trade-offs with other ESs, while the remaining ESs displayed varying degrees of synergistic relationships. Nonetheless, it should be noted that transforming extensive farmland and impervious land into diverse land-use types might not improve the synergies relationship of ESs. Additionally, the full protection scenario (FPS) demonstrated greater advantages in terms of HQ, WC, and CS.