Abstract: Food organisms play a key role between prey and predator in the marine ecosystem. Based on the stable isotope signatures, a study of seasonal trophic niche variation and inter-species competition of food organisms from south-central East China Sea was conducted in November 2018 and April 2019. Our study confirmed a wide range of stable isotope signatures, indicating a high level of food sources diversity and a stable nutrition structure in study area of south-central East China Sea. Significant variations were confirmed by δ¹³C and δ¹⁵N values of samples in addition to seasonal changed trophic levels. Moreover, our study verified the seasonal variations of trophic niches of fishes, shrimps, and cephalopods due to the environmental changes and dietary shifts. Our results provide evidence of the temporal variations of trophic niches in food organisms. And it is hoping that this research could provide a scientific basis for the sustainable exploitation of fishery resources and the protection of ecological environment in the East China Sea.