Abstract: Based on fishery resource survey data, Ecopath models were constructed before and after the fishing ban in Poyang Lake (2018 and 2021) to evaluate the effectiveness of the “10-Year Fishing Ban” policy on ecosystem. Comparisons were made regarding differences in ecosystem scale, food web and nutrient structure, energy flow characteristics, and system stability between the two periods. The results indicate a notable expansion in the scale of the ecosystem by 8.07%, accompanied by a substantial increase in total biomass by 35.7%. Moreover, the energy and material transfer efficiency of the ecosystem experienced an improvement from 10.7% to 11.3%, which is close to the historical level of 1998 (11%). Furthermore, there was an enhancement in ecosystem maturity and stability. The high nutritional index of the food web increased from 28.6% to 35.7%, while the length of the food chain increased from 3.63 to 3.86. In summary, following the fishing ban, the Poyang Lake ecosystem exhibited increased complexity, stability, and maturity, with stronger nutritional interactions among various functional groups. The speed of material circulation and the proportion of material recycling in the ecosystem also increased, indicating that the “10-Year Fishing Ban” policy has achieved significant positive outcomes.