From 2020 to 2024, a fish survey was conducted in four sections (i.e., Luoguhe Village, Kaikukang, Huma, Heihe) and several tributaries in upper reaches of the Heilongjiang River. According to the survey statistics, 67 fish species live in these areas, consisting of 8 orders, 14 families, and 49 genera. Among them, 39 species belong to the Cyprinidae family, accounting for 58.21% of the total species number and making this family the biggest one in the fish community. Eight species belong to the loach family, contributing to 10.45% of the total species number and making it the second biggest family. Additionally, seven of the 67 fish species have been recognized as endangered species, including the national first-class protected wild animal Huso dauricus, the national second-class protected wild animal Acipenser schrencki, Brachymystax lenok, Hucho taimen, Lampetra japonica, Lampetra reissneri and Thymallus tugarinae; Furthermore, Lampetra japonica is a newly recorded species in the upper reaches of the Heilongjiang River. In the autumn of 2020, species diversity index (Hʹ) ranged from 1.81 to 2.47 for the fish community in the upper reaches of Heilongjiang Province, while its richness index (Dʹ) and evenness index (Jʹ) ranged from 1.52 to 2.78 and 0.60 to 0.74, respectively. Fish composition of the study areas varied with space and season, with the Heihe River section having the highest fish species richness and relatively high dominant species abundance. Meanwhile, fish species composition in the Heihe River section differed a lot between spring and autumn. These results provide fundamental information for the protection, management, and utilization of fish resources in the upper reaches of the Heilongjiang River.