| Guijiang River is the primary tributary of Xijiang River, with a total length of 438 km and water area of 18,790 km2. In this study, we investigated the current status of fish resources in Xijiang River, focusing the field investigation on species composition, dominant species and spatio-temporal variations. The objectives were to provide scientific evidence for conserving biodiversity, sustainable development of fish resources and support the evaluation of river system health. In January, April, July and October of 2015, the investigation was conducted at nine sampling sites, representing different habitats; Pingle (S1), Zhaoping (S2), Wujang (S3), Majiang (S4), Muge (S5), Dalang (S6), Jingnan (S7), Daoshui (S8), Wuzhou (S9). Fish samples were collected using portable fishing equipment and nets, and all fish collected were identified by species. A total of 93 fish species were collected, falling into 166 genera, 7 families and 6 orders. Cypriniformes (63 species, 3 families) dominated the fish collected, accounting for 67.74% of the total species, followed by Perciformes (15 species, 8 families, 16.13%), Siluriformes (12 species, 3 families, 12.90%), Synbranchiformes (1species, 1 family, 1.07%), Anguilliformes (1 species, 1 family, 1.07%) and Cyprinodontiformes (1 species, 1 family, 1.07%). Hemiculter leucisculus was the most dominant species over the study period [relative density (RD) of 12.75%], but the dominant species varied with season; : Hemiculterella wui, Hemiculter leucisculus and Zacco platypus in winter; Hemiculter leucisculus, Sinibrama macrops and Pseudohemiculter dispar in summer; Hemiculter leucisculus, Tilapia mossambicus and Tilapia niloticus in autumn and no dominant species evident in spring. Non-metric multidimensional scaling (NMDS) ordination and one-way analysis of similarity (ANOSIM) showed that the fish community structure varied significantly with season (P<0.05), except for between summer (July) and autumn (October) (P=0.178>0.05). Structural differences were attributed to the effects of breeding season in the Pearl River (April-June) and seasonal variation in precipitation along the Guijiang River. Spatially, there were significant differences in the fish community between S1 and S7, S1 and S8, S1 and S9; S6 and S7, S6 and S8, S6 and S9; S2 and S6, S2 and S9. The static and deep water environment of reservoir after hydropower development, and alien species invasion were the primary factors leading to spatial changes in fish community structure.