The Taiwan Strait, located between the South China Sea and the East China Sea, is an important channel for migratory fishes between the two waters, and therefore has a unique and high diversity of fish species due to its spatial marine environment. However, the rapid development of coastal aquaculture and excessive exploitation of natural resources has resulted in habitat degradation, and the ecosystem has been reverting to a low stage of development. Understanding the relationships between environmental factors and fish assemblages is thus essential for sustainable exploitation of fish resources. In this paper, fish species composition, dominant species, fauna characteristics, species diversity and spatial distribution in the Taiwan Strait and its adjacent waters were studied using data collected from bottom trawl surveys in summer(July) 2014. We also identified the spatial structures of fish assemblages and their relationships with environmental variables. In total, 84 fish species were captured in the survey, belonging to 69 genera, 48 families and 16 orders; these were mainly composed of warm-water, continental shelf demersal fish and continental shelf reef-associated fishes. The primary dominant species were with an average biomass of 33.84 kg/h and 31.56 kg/h, respectively. Cumulative biomass accounted for 46.92% of total fish biomass, and the regression contribution of the biomass to total biomass was 0.30 and 0.62, respectively. High biomass of the dominant species was mainly distributed in the offshore waters of the northern Taiwan Strait, an obvious overlapping of ecological spatial niche. According to hierarchical cluster analysis,fish assemblages were classified into two groups:a coastal community dominated by coastal species such as ; and a widespread community dominated by species such as Trichiurus japonicas, Tentoriceps cristatus, Benthosema pterotum, Trachurus japonicas, Psenopsis anomala and . Diversity analysis showed that the Shannon-Wiener diversity index ' ranged between 0.22 and 2.31 with a mean of 1.44; the Pielou evenness index ranged from 0.11 to 0.72 with a mean of 0.51; and the Margalef species richness index ranged from 0.36 to 4.04 with a mean of 1.59. Significant linear negative correlation existed between the Margalef species richness index and total biomass. A positive correlation with water depth was also found, which indicated that the Margalef species richness index rose with depth, but decreased as biomass increased. Canonical correspondence analysis suggested that the main environmental factors affecting the spatial patterns of the fish assemblage in summer were bottom water salinity, inorganic nitrogen, temperature and temperature difference between surface layer and bottom layer. However, the main environmental factors affecting the spatial patterns of the dominant fish assemblage were bottom water salinity, temperature and inorganic nitrogen.