Abstract:Dense fern understory (DFU) is widespread in forests, especially in disturbed forests, which has a strong filtering effect on tree species regeneration and can change the diversity of understory and affect the structure, function and dynamics of forest community. Thus, ecological studies on DFU are vital to reveal the distribution patterns of species and the community assembly rules. Combined with the latest studies at worldwide, the characteristics of DFU was summarized, and the main reason for the formation of DFU was explained by mechanism. The pathways of DFU effect on the forest regeneration through resource competition, allelopathy animal feeding strategies and mechanical interference were described. The potential influence of DFU on the forest succession was also discussed. Finally, several shortcomings of current studies of DFU were identified.