Based on the bottom trawl survey data by R/V "Beidou" from September, 2006 to May, 2007 in the sections of the central and southern Yellow Sea, fish community structure, community diversity, biomass distribution by catch per hour and their relationships with environmental variables were studied. A total of 109 species were collected, all of which were Osteichthyes, belonging to 86 genera, 57 families, and 16 orders. The most species-rich orders were Perciformes (45 species), followed by Scorpaeniformes (12 species), Clupeiformes (10 species), and Pleuronectiformes (10 species). The fish catch was dominated by warm water species and warm temperate species, including few cold temperate species. The proportion of species ecotypes in fish catch varied with survey time, e.g., warm water species dominated the catch in March 2007 and warm temperate species dominated the catch in September 2006. The majority of species were small-sized pelagic (e.g., Engraulis japonicus, Setipinna taty) and low-valued demersal species (e.g., Lophius litulon, Liparis tanakai), excluding Larimichthys polyactis, Trichiurus lepturus, and Pampus argenteus. Engraulis japonicus was the dominant species during four surveys, but its proportion in the total catch varied significantly with survey time. The important species composition, excluding Engraulis japonicus, Setipinna taty, Lophius litulon, and Liparis tanakai, varied rapidly during survey time, as well among the different survey areas. The important species accounted for >85% of the total catch in every survey area, and the dominant species accounted for 50% of the total catch in every area. The trophic level of fish caught in the central and southern Yellow Sea was 4.2-4.5, 3.0-3.3 and 3.6-3.9. The trophic level of the catch varied among areas, and within an area over time. These changes were closely related to the population structure in each area, and the temporal and spatial distribution of prey organisms. For example, the juveniles (which feed primarily on zooplankton) were the dominant component of the total catch in May. A shift in the trophic level as the fish grew and their feeding ecology changed. The size spectra of fish was variable (3-24 cm), particularly in section S2, and the size spectra tended to increase from the south to north, associated with differences in fish community structure and fish biological characteristics. In addition, the size spectra varied within areas over time. There was a higher proportion of individuals >48 cm in December, 2006 whereas individuals <3 cm contributed a higher proportion in May, 2007. These changes were associated with the spawning, feeding, and overwintering migrations. The majority of species spawn in May, during which time the recruiting individuals dominated the catch. Conversely, the fish catch in December was dominated by overwintering species, which were found in the changes of the size spectra of Lophius litulon, Liparis tanakai, Engraulis japonicus, Setipinna taty, and Larimichthys polyactis. There was no significant difference in the diversity indices among the sections of central and southern Yellow Sea, and section S2 and S3 were particularly comparable. Based on a comparison of historical data, there appears to be a decreasing trend in fish diversity in the central and southern Yellow Sea. Analysis of the relationships between diversity indices and environmental variables suggested that the number of fish species and diversity indices were positively correlated with sea bottom temperature, and negatively correlated with water depth.