The Gaoligong Mountains are a hotspot of biodiversity in China. Mid-mountain humid evergreen broad-leaved forests are the most widely distributed and best-preserved vegetation type in the region. Plant seedlings are an important stage for community regeneration. The species composition and dynamics of seedlings is of great significance for the conservation and management of local forest resources. However, there are still few studies that explore the characteristics of seedlings in the region. To solve this problem, seedlings were measured, tagged and identified in November 2020 and re-censused regularly every six months in a four-ha forest dynamic plot in a mid-mountain humid evergreen broad-leaved forest in the Gaoligong Mountains. The species composition, spatial distribution, and dynamics of the seedlings in the plot were investigated. The results showed that 977 seedlings belonging to 56 species in 44 genera and 23 families were recorded in the four censuses. The dominant species were obvious, and most of the species were rare species. The seedlings of most species were unevenly distributed in the plot, and Psychotria morindoides was the most widely distributed. The fluctuations in the number and species composition of the seedlings were small. In summary, the structure of the seedlings was stable in the mid-mountain humid evergreen broad-leaved forest in the Gaoligong Mountains.