To comprehend the fish assemblage characteristics of the rocky reef habitats in the sea area of Dachen Islands， we collected fish samples from the subtidal rocky reef habitats using gillnets with multiple mesh， once per season from September 2020 to April 2021. Multiple statistical methods， including Jaccard similarity index， relative importance index， α-diversity index， clustering and ordination， and canonical correspondence analysis， were employed to investigate the characteristics of fish assemblages in this habitat and their relationship with environmental factors. A total of 49 fish species were collected from the subtidal rocky reef habitats of Dachen Islands. These species belong to 10 orders， 27 families， and 40 genera. The highest proportions were found in the Sciaenidae family （22.45%） and the Engraulidae family （10.20%）. Eleven dominant species appeared throughout the year， with Sebastiscus marmoratus， Johnius distinctus， and Stephanolepis cirrhifer exhibiting high dominance. The multivariate statistics results indicate significant spatial and temporal differences in fish communities in subtidal reef habitats on Dachen Islands. Different degrees of dissimilarity between various site types were observed， with the aquaculture areas and eastern rocky reefs forming assemblages that differed significantly from other areas （P<0.05）. Additionally， significant seasonal variations were observed （P<0.05）， with the highest biological diversity observed in summer and the lowest in winter. Canonical correspondence analysis identifies salinity and temperature as the most significant factors influencing fish assemblages in the rocky reef habitats of Dachen Islands. On a local scale， the study reveals that rocky reef habitats around aquaculture disturbance areas exhibit more stable and diverse fish assemblage patterns. The negative impact of aquaculture activities on fish assemblages is currently not significant， and fish within these habitats may have already developed adaptive strategies to cope with human disturbances. But in general， the fish assemblage composition of subtidal reefs was simple and structurally fragile， emphasizing the urgent need for targeted conservation and management measures.