Hydropower plant operation changes river habitats in various aspects, and thus affects the community composition of the river ecosystem. As a result, the river health is adversely affected. The influence of a hydropower plant cascade on river continuity is even more pronounced. In this study, benthic macroinvertebrates and environmental factors were sampled from the Jingbohu Hydropower Plant to the Shiyan Hydropower Plant, along the Mudan River, and the influence of a hydropower plant cascade on the longitudinal distribution of benthic macroinvertebrates was analyzed. The results demonstrate that the hydropower plant cascade affected several environmental variables and led to changes in the community composition of benthic macroinvertebrates in the Mudan River. Significant differences were observed between sites upstream and downstream of the hydropower plants, with more sensitive species downstream of the hydropower plants. "Run-of-river" hydropower plants exert less adverse influence on benthic macroinvertebrates than dam-type plants. The influence of hydropower plants decreases along the longitudinal direction of the river, with the density and richness of benthic macroinvertebrates increasing.