Marine ranching is an ecological system engineering with many functional areas. The ecological environment and food web structure vary from functional area to functional area. Study on food web structure of different functional areas contributes to knowing ecosystem differences among functional areas. Stable isotope techniques were applied to the analysis of food web structure in different functional areas in Nan'ao Zhelin Bay Marine Ranch, where samples were collected for fishery resources and environment investigation. The results showed that 78 species were collected in the marine ranching, the δ¹³C values of consumer ranged from -19.94‰ to -13.62‰, the δ¹⁵N values ranged from 8.78‰ to 15.29‰ and trophic level ranged from 1.73 to 3.64. Compared with other functional areas, the artificial reef area possessed more biological resources and complex structure of food web. In addition, there is broader isotopic resource and higher trophic redundancy in macroalgae area while the ecological niche of shellfish area was narrower and nutrient distribution was more concentrated. By comparison of the ecosystem stability in different functional areas, the artificial reef area is best while the macroalgae area is poor.