Based on fishery survey data from the Hui-bie-yang sea area of Hangzhou Bay in the autumns of 2015 and 2017, the ecological relationship between major nekton was analyzed via niche breadth, niche overlap, cluster analysis, W-test, χ²-test, association coefficient (AC), and percentage of co-occurrence (PC). The results showed that there were 21 major nekton species in this area; of which, the dominant species were Harpodon nehereus and Exopalaemon annandalei, whose niche widths occupied the top two. Based on the niche breadth cluster analysis, the major nekton species were divided into three groups:wide niche breadth species, moderate niche breadth, and narrow niche breadth species. The niche overlap values varied from 0-0.93, which shows marked difference, indicating that the species had a similarity of ability in using resources, and there was a certain degree of competition between species. The VR and W results showed that the major nekton species were significantly positively correlated. The χ²-test suggested that there were significantly interspecific associations for 105 species pairs (χ² ≥ 3.841). The results of AC and PC revealed that the association of interspecificity was strong, and tended to be positive correlation.