Fish is the primary focus of research within fishery resources and represents one of the most important sources of human food. Within the fishery ecosystem, the fish community can reflect the energy conversion processes. The southern Yellow Sea, characterized by the interplay of the Yellow Sea warm current, coastal current, and the Yellow Sea cold water mass, possesses a complex ecological environment and abundant fish resources. To comprehend the composition and characteristics of the fish community and the spectrum of fish biomass particle sizes in the southern Yellow Sea, we conducted an analysis using trawl survey data from 2017 to 2018. Our study examined fish species composition, dominant species, and resource density across four seasons and constructed a fish biomass particle size spectrum. The findings revealed that a total of 133 fish species from 64 families and 20 orders were collected. The dominant species included Larimichthys polyactis, Pampus argenteus, Engraulis japonicus, and Trichiurus lepturus, with some differences in dominant species across different seasons. The annual average resource density of fish was (1258.85±796.92) kg/km² , with seasonal variations observed in summer, spring, autumn, and winter. An ABC curve indicated significant disturbance in fish communities during spring and autumn, with moderate disturbance during summer and winter. Notably, distinct seasonal differences were found in the Sheldon-type particle size spectrum of fish, with high abundance among small-sized individuals at specific particle size levels corresponding to peaks. Furthermore, the fitting curve for the standardized fish biomass particle size spectrum exhibited a parabolic shape with curvatures higher than the stable theoretical value –1. This suggests dominance by small individuals within the fish community and low nutrient cycling efficiency. Overall, the instability of the fish community in the southern Yellow Sea may be attributed to environmental factors, the physiological habits of fishes, and human fishing practices.