In this study, we analyzed the stomach contents of main fishes collected using a bottom trawling net in the offshore waters of southern Zhejiang, China from 2016 to 2019. By combining with the data of early feeding habits, we constructed the food web topology of the fish community based on interspecific trophic relationships. The keystone species of the fish community was determined using the topological network index and KPP calculation. The results showed that there were 276 pairs of trophic links in the food web based on the feeding analysis. Trichiurus lepturus with the highest D, D_in, CC, BC, and IC and Benthosema pterotum with the highest D_out, TI¹ , and TI⁹ had the highest rank among the 34 species, indicating that they were closely related to other species in the fish community and could control the stability of community structure and information diffusion. The key index of T. lepturus (K and K_t) and B. pterotum (K_b) had the highest value, indicating that they played a decisive role in the energy flow and information transfer of community structure. It was verified using KPP calculation that T. lepturus played a decisive role in the stability of fish community structure and the transmission of interspecific information in the offshore waters of southern Zhejiang. In this study, the keystone species of the fish community were identified using 11 topological parameters combined with KPP calculation. It was found that T. lepturus (D, D_in, CC, BC, IC, K, and K_t) and B. pterotum (D_out, TI¹ , TI⁹ , and K_b) played a key role in the stability of community structure, in which T. lepturus was the keystone predator and B. pterotum was the keystone prey.