Abstract: To clarify the resource allocation strategies of four types of economic octopuses in the East China Sea (Amphioctopus fangsiao, A. ovulum, Octopus minor, and O. sinensis), we conducted a systematic analysis of their nutritional ecological niches using stable isotope techniques (δ¹³C and δ¹⁵N). We selected 193 octopus samples collected from the northern East China Sea during 2021—2022. According to the δ¹³C and δ¹⁵N values, as well as the differences in sex among different species, we constructed the ecological niche standard ellipses for the four octopus species, and their intra-species male and female populations. Through the analysis of standard ellipse area and overlap rates, we observed the inter-species and intra-species differentiation characteristics of nutritional ecological niches. The results show significant differences in δ¹³C values among the four octopus species (p<0.01), with O. minor (−17.08±0.88)‰ and O. sinensis (−16.52±0.87)‰ showing significantly lower values than A. fangsiao (−17.87±0.87)‰ and A. ovulum (−17.37±0.84)‰, reflecting distinct feeding preferences. Furthermore, there were significant differences in δ¹⁵N values among the four species (p<0.01), indicating clear nutritional level stratification. The ecological niche width of O. sinensis was the largest, possessing the greatest standard ellipse area (SEAc) and demonstrating a diverse resource utilization approach, while O. minor relied on a singular benthic food resource. Sexual differences were significant in certain species, particularly in O. sinensis, where a significant difference in δ15N values was observed between male and female individuals (p<0.01), indicating considerable disparities in their nutritional levels. The study concludes that the four octopus species in the East China Sea achieved coexistence through source differentiation (δ¹³C) and the differences in nutritional levels between male and female O. sinensis (δ¹⁵N), with a niche overlap rate of 27.74%.