We evaluated the trophic ecology of fish on the Xuwen Coral reef. We collected samples of representative species and quantified levels of δ¹³C and δ¹⁵N. There was significant variation in the δ¹³C and δ¹⁵N values. δ¹³C ranged from –20.98 and δ¹⁵N ranged from 11.66. The levels of δ¹³C and δ¹⁵N were generally higher than in fish from other regions. We estimated the trophic level based on the δ¹⁵N values. The majority of fish species in the Xuwen Coral Reef were lower and mid-level carnivores. The remainder were omnivores and higher carnivores. Among all fish species, more than half were lower carnivores (70 species, 52% of the total species). The mid-level carnivores (47 species) accounted for 35% of the total species. The omnivores (11 species) and higher carnivores (8 species) accounted for 8 and 5%, respectively, of the total species count. We compared these results to those of gut-contents analysis for 54 species. For the majority of species (85%), the trophic level estimated by the two methods differed by less than 0.5 units. Thus, stable isotope analysis provides a rapid, reliable method for documenting ocean food webs.