To evaluate the ecological carrying capacity of in Daya Bay, we constructed an ecopath model comprised of 26 functional groups of Daya Bay. The model was based on the survey data of fishery resources and the ecological environment of Daya Bay in 2015 using Ecopath with Ecosim 6.5 (EwE). The general characteristics of the Daya Bay ecosystem were analyzed, and the ecological carrying capacity of was predicted combining food web structure and energy flow. The results indicated that the trophic level of was 3.44 and its ecotrophic efficiency was 0.302. Trophic levels of the functional groups varied from 1 to 3.95. Total transfer efficiency was 7.636% and the ratio of total primary production to total respiration was 2.142. Connectance index and system omnivory index were 0.364 and 0.210, respectively. The results implied that each trophic level transfer efficiency was low, and the energy was not fully taken advantage of. Energy flow to detritus of trophic level I and Ⅱ was 98.11% of that to total detritus, signifying that energy transfer was hindered and that the system has a potential for continuous enhancement. Ecological carrying capacity of , 1.4 times the amount of biomass at present. Meanwhile, the ecotrophic efficiency of other planktivorous fishes equaled 1.000, suggesting that the ecosystem was balanced. When reaching the ecological carrying capacity of , the ratio of total primary production to total respiration changed marginally (variation value is 0.001), while system omnivory index and system connectance index were unchanged. Thus, the stability and structure of the ecosystem of Daya Bay was not altered significantly.