Research on Fern Diversity (Pteridophyta) In Bemban village In Mount Ambawang Protected Forest Kubu Kubu Raya District of West Kalimantan Province was held on September 16 th to October 7 th , 2013. Sampling plot was taken purposive where there were many fern found. There were four sampling plot based on height. Plot I located in 50-150 m above sea level altitude, plot II in 150-250 m above sea level altitude, plot III in 250-350 m above sea level altitude,and plot IV in 50-150 m above sea level altitude (rubber plantations). Each sampling plot 40 m x 40 m, divided into 160 subplot 2 m x 5 m aech. There were 13 fern species with 4162 individual these species consist of 8 terresterial fern with 3799 individual, and 5 epiphytic fern with 813 individuals. The plot at altitude of 50-150 m,were dominated by Lygodium circinatum and Asplenium nidus, altitude 150-250 m were dominated by Acrostichum spesiocum and Asplenium nidus, altitude 250-350 m dominated by Selaginella wildenowii, Asplenium longisimmum height of 50-150 m asl (rubber plantation) dominated by Nephrolepis biserrata and Asplenium nidus. The highest diversity index value was at altitude 150-250 m (2,043) which means the species diversity of ferns were low. Similarity index was highest between altitude 250-350 m and altitde 50-150 m in rubber plantation,in the value 5,638 %. It means between thw different plot there is no similarity (¤ 25 %). Keywords: Ferns, biodiversity, forest protected mount Ambaw
