During the investigating field, the authors find out 126 species of fern belong to 28 families in 4 phyllum in Kon Ka Kinh National Park. Among them Psilotophyta has 1 family, Lycopodiophyta has 2 families, Equysetophyta has 1 family and Polypodiophyta has 24 families. Some rich families such asPolypodiaceae (26 species), Dennstaedtiaceae (9 species), Dryopteridaceae and Lycopodiaceae (8 species). Some rich general such as Pleris and Asplenium (7 species), Pyrrosia and Cofysis (5 species)... The fern distributed in many habitat types but mainly along the stream, wet soil, under the shadow... Many species are rarely in Kon Ka Kinh national park. State of the fern in Kon Ka Kinh National Park with many population reduction observed. Such as Cibotium barometz for medicinal and ornamental. Because of it's root's beautiful and strange-looking, they are non rational exploited by human. In the other hand, Drynaria bonii and D. fortunei for medicinal. They have only small population, individual poor quality, they are in Red Data Book Vietnam (2007). Some of species in Cyathea and Marattia are the same state. Up to now, fern have to opposite to be in danger. The author need some conservation measures them as soon as possible.