Abstract: Filter-feeding shellfish and macroalgae play significant roles in food production and ecological regulation within integrated multi-trophic aquaculture (IMTA) systems. To investigate the effects of polyculture of oysters (Crassostrea rivularis) and macroalgae (Gracilaria verrucosa) on the aquaculture performance of large yellow croaker (Larimichthys crocea), we compared the impacts of monoculture (Fish-only) and different IMTA modes (Fish-shellfish, fish-algae, and fish-shellfish-algae polyculture) on the water quality and growth of large yellow croaker. The results showed that IMTA models significantly improved water quality and promoted the growth of L. crocea. The contents of ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), nitrous nitrogen (NO₂⁻-N) and active phosphate (PO₄³⁻-P) in the fish monoculture system increased significantly along with time, while the IMTA systems (Especially the fish-shellfish-algae polyculture) reduced the accumulation of nutrients in the water through the synergistic effect of oysters and Gracilaria. Among them, the contents of NH₄⁺-N and NO₃⁻-N at the mid-to-late culture stages of fish-shellfish-algae (LOC212 group) were (1.94±0.11) and (2.83±0.28) mg·L⁻¹, compared with the monoculture systems (3.40±0.31), (6.51±0.98) mg·L⁻¹ were significantly reduced by 42.76% and 56.49% (p<0.05). Additionally, the dissolved oxygen and water transparency in IMTA systems were significantly higher than in the monoculture systems during the mid-to-late culture stages. In terms of growth performance, the survival rate (98.33±2.89)% and body mass gain rate (5.91±3.31)% of L. crocea in fish-shellfish-algae polyculture were significantly higher than those in monoculture group (p<0.05), indicating that the synergistic effect of fish-shellfish-algae was more conducive to the growth of L. crocea. In conclusion, the IMTA model achieves the dual goals of water quality regulation and growth optimization through the synergistic effect of multiple trophic levels, providing an ecologically efficient aquaculture strategy for L. crocea in southern regions.