Headwater streams are critical locations with nutrient recycling and energy flow along a river ecosystem, posing vital significance to macroinvertebrate biodiversity maintenance in rivers. However, in China, research upon headwater streams' macroinvertebrate community structure is few, and the report about seasonality of macroinvertebrate community structure in headwater streams of the Changbai Mountains is particularly lacking. By using in-situ sampling in the wild, we attempt to elucidate seasonality of river macroinvertebrates and the major environmental drivers behind in headwater streams of the Changbai Mountains. The results revealed:(1) A total of 90 taxa of river macroinvertebrates were identified, pertaining to 3 classes, 9 orders, and 38 families. Among which, aquatic insects (85 genera) were dominant. Seasonality of the river macroinvertebrates' community structure was manifest, with density and diversity of the macroinvertebrates significantly higher in fall and summer than in winter and spring, reaching minimums in winter. (2) Gather-collectors were dominant functional feeding groups, and then shredders, predators, and scrapers. By contrast, filter-collectors accounted for a little part. The seasonality of different functional feeding groups indicated not in line with each other, despite density and species richness all demonstrated highest in autumn. (3) Water temperature, distribution of leaf litter, and flow velocity were major drivers of seasonal dynamics of river macroinvertebrate communities in the area. Our results may provide a support for addressing the headwater streams ecology in the Changbai Mountains, and ecological restorations of the Songhua River basins.