The marine ranching area of Wuzhizhou Island in Sanya has achieved good results in terms of coral reef restoration and tropical marine ranching construction, but the nutritional structure and stability of the ecosystem in the ranch area still need long-term monitoring and evaluation. Based on the stable isotope technology of carbon (δ¹³C) and nitrogen (δ¹⁵N), the regional food web of the Wuzhizhou Island Marine Ranching in Sanya was constructed and studied for the first time. In July 2020, the marine biology survey collected 52 major consumers. The results revealed that the δ¹³C values of the dominant consumers ranged from -19.10‰ to -12.74‰ (with an average of (-16.99±1.52)‰). The δ¹⁵N values of the dominant consumers ranged from 6.43‰ to -14.03‰ (with an average of (11.24±1.70)‰). One-way analysis of variance (ANOVA) showed that the stable carbon and nitrogen isotopes of different groups were significantly different (P < 0.01). The contribution rate of macroalgae and benthic microalgae to major consumers was 41.50%. Sedimentation organic matter (SOM) and phytoplankton were also important carbon sources for consumers (contribution rates are 20.05% and 19.97% respectively). Suspended particulate organic matter (POM) contributed the lowest carbon source to consumers by 18.48%. The nutritional level of the main consumers in the Wuzhizhou Island Ranch area in Sanya ranged from 1.53 to 3.76. The nutrition level of major consumers was less at both ends and more in the middle. Hierarchical cluster analysis showed 4 trophic groups in marine ranching area of Wuzhizhou Island in Sanya. The first group was mainly composed of mixed-feeding benthic fishes and cephalopods; the second group was shrimp and crabs eating mainly benthic microalgae, and SOM as the supplement; the food source of the third group was mainly macroalgae, especially carnivorous fish; the fourth group was SOM and primary consumers eating on benthic algae (e.g. echinoderms and gastropod). The SIBER model was used to analyze the nutritional structure indicators of the Wuzhizhou Island pasture ecosystem in Sanya. Compared with the results in the adjacent sea areas, it was found that the level of food source diversity (CR), trophic level length (NR), total area (TA) and mean distance to centroid (CD) were relatively high; and the nutritional redundancy (MNND, SDNND) of the food web in the research sea area was relatively high. This study initially constructed a food web for the marine ranching area of Wuzhizhou Island in Sanya to provide basic information and reference data for understanding the nutritional structure of the ecosystem.