Xiangshan Bay is a semi-closed bay in the central coast of Zhejiang Province, China. It is also a centralized distribution area of various fishery resources, and many economic fish species breeding there every year. However, due to long-term overfishing, ocean development and environmental pollution, deterioration of ecological environment was found in this sea area, which also caused the increasingly recession of local fishery resources. In recent years, after fishery resources conservation, fishery resources in this water have been restored. It also provides a good habitat for reef-loving species such as the black sea bream Acanthopagrus schlegelii. A. schlegelii is an important fish species targeted by recreational and commercial fisheries in Xiangshan Bay. Maintaining population stability of this species is economically and ecologically important for the embayment. Knowledge of the feeding ecology is of great value for conservation strategies, as it is thoroughly linked to subjects such as resource partitioning, habitat preferences, prey selection, predation, competition and energy transfer within and between ecosystems. However, relatively little work has been done on this aspect in A. schlegelii. In this study, 21 individuals of A. schlegelii were collected in Xiangshan Bay, and diet composition and feeding habits were analyzed by high-throughput sequencing methods targeting 18S rDNA gene. By Illumina high-throughput sequencing, 913,254 target fragments with length of about 420 bp were obtained. The minimum sequence number of samples was 30,826, while the maximum one was 52,374. A total of 554 OTU (operational taxonomic units) were obtained from 21 samples after clustering. And 62 species in 9 categories were identified in the stomach contents of this species after sequence alignment, in which Mollusca, Arthropoda and Chlorophyta exhibited the highest abundance, followed by Chordata, Platyhelminthes, Bacillariophyta and Annelida. Ulva lactuca, Crassostrea sikamea, Centropages hamatus, Charybdis japonica, Scapharca subcrenata and Sebastiscus marmoratus were dominant prey items for A. schlegelii in Xiangshan Bay. The above prey items accounted for 60.90% of the total abundance of gastric contents. In addition, a number of species, including Caprella scaura, Oithona sp., Melosira sp., Cyclotella sp., Chlorella stigmatophora, Picochlorum sp., Torodinium robustum, and Chromadorina sp., with quite low abundance were also detected. These prey items were distributed in different ecological communities, including macroalgae, shellfish, zooplankton, phytoplankton, macrozoobenthos, fish, and crab. These data suggests that A. schlegelii is a relatively large omnivorous consumer. Result from the analysis of similarities (ANOSIM) showed no significant difference in diet composition for fish among different age groups. This indicates that A. schlegelii did not alter feeding habits after 1 year old. Considering the limited sample size, however, further studies are still needed to address this conclusion. Compared with the traditional analysis methods, high-throughput sequencing has the characteristics of less sample demand, less workload, and more species detection. Meanwhile, due to its sensitivity, some species with low abundance that could not be found by traditional methods can also be detected. Hence, high-throughput sequencing technology has obvious advantages in fish diet studies and can provide strong support for marine organisms feeding and ecological studies.