This study investigated the niche and interspecific associations of shellfish, as well as the impact of environmental factors on the niche differentiation of dominant species in shellfish, based on four quarters of benthic shellfish biomass and marine environment survey data conducted in the coastal waters of Zhejiang from August 2020 to April 2021. The results showed that a total of 41 species of shellfish were surveyed and collected, of which 16 were the main shellfish, divided into three ecological groups. The niche width was 1.1–3.7, with an average of 2.4. Among the shellfish, Bursa rana had the largest niche width of 3.7, and Phalium bisulcatum had the lowest of 1.1. The niche overlap value between species was 0–0.66, with the maximum niche overlap value between species of Fusinus longicaudus and Hemifusus tuba being 0.66. The niche overlap between 58 species was 0, and the degree of niche overlap was relatively low. The overall correlation between the main shellfish species was not significant (VR＞1), and 89.7% of the species showed no significant correlation (P＞0.05), indicating that the overall competition for resources among the major shellfish species in the sea area was relatively low. However, some species such as Turritella terebra bacillum, Glossaulax didyma, Tonna olearium, and Bursa rana also had strong competitive relationships. The environmental factors that affected the niche differentiation of dominant species of shellfish in different seasons were slightly different; however, the major factors affecting the niche differentiation of nearshore shellfish are habitat water depth and salinity (0.2≤r＜0.4, P＜0.01). These results can provide a scientific basis for the assessment of ecological stability and resource conservation of nearshore shellfish.