Abstract: In order to investigate the trophic structure characteristics and spatiotemporal variations of aquatic communities in the Hun-Tai River, an important branch of the Liaohe River, the fishery resources surveys were conducted in autumn (October) 2020 and spring (May) 2021. Based on stable isotope analysis, the δ¹³C and δ¹⁵N values of dominant consumers and basal food sources in the river were determined. Then the spatiotemporal variations of trophic structures and the contributions of the basal carbon sources to the aquatic food web were analyzed by SIBER and MixSIAR package. In our study, a total of 23 species of catches, belonging to 3 orders, 6 families, and 20 genera were collected. All the δ¹³C and δ¹⁵N values of the main catches ranged widely from –37.18‰ to –19.28‰, 7.98‰ to 16.51‰, respectively. There were no significant seasonal differences in δ¹³C and δ¹⁵N values (P>0.05). However, the δ¹³C values variations of spatiality were significant (P<0.01), and the carnivorous δ¹⁵N values were higher than omnivorous (P<0.05). The trophic level of catches, ranging from 1.71 to 4.39 in the Hun-Tai River, had extremely significant temporal and spatial differences (P<0.01). The comparison of the ecosystem trophic structure revealed that the food resources and ecological niche occupied by fish in autumn were higher and broader than that in spring, and all trophic structure indicators (NR/CR/TA/CD/NND/SDNND) of the Taizi River higher than those of the Hun River might be brought out by the higher degree of exploitation in the Hun River. In addition, the basal food sources analysis results supposed that aquatic plants and terrestrial plants were major carbon sources in autumn and spring, respectively. Meanwhile the terrestrial plants and POM were major carbon sources in the Hun River and Taizi River, respectively. This study of enriching the contents about food web in the Hun-Tai River provided references for the subsequent protection, restoration and further development, and accumulated basic data for the reconstruction of the river ecosystem in Northeast China.