Abstract: To systematically understand the seasonal dynamics and assembly mechanism of macroinvertebrate community in Huishui River, an investigation was carried out in October (autumn) and December (winter) 2021, April (spring) and August (summer) 2022. The Huishui River supports a high array of macroinvertebrate diversity. A total of 168 taxa were identified, belonging to 8 classes and 73 families. The numbers of macroinvertebrate species in spring, summer, autumn and winter were 85, 77, 82 and 82, respectively. Analysis of similarities (ANOSIM) and nonmetric multidimensional scaling analysis (NMDS) showed that the macroinvertebrate community structure in Huishui River differed significantly among seasons. Canonical correspondence analysis (CCA) showed that the environmental factors affecting the macroinvertebrate community structure were different in the four seasons. Environmental filtering appeared to be key process in structuring macroinvertebrate assemblages in spring, autumn and winter, while the spatial processes played a leading role in summer. This study provides an important scientific reference for the seasonal dynamics of the macroinvertebrate community structure, biodiversity assessment and environmental monitoring in the mountainous streams of southern Anhui Province.