Abstract: Triarrhena is a small-sized gunus of Gramineae with only two species,which occurs in eastern Asia,particularly in China,but its taxonomic treatment has been a controversial matter.It was treated as an independent gunus,or a species under Miscauthus or Imperata.This study is to assess the phylogeny of Triarrhena and its related genera in Saccharinae(Gramineae) based on internal transcribed spacer(ITS) and the 5.8s coding region of the nuclear ribosomal DNA.Maximum parsimony(MP) and neighbor-joining(NJ) methods were employed to analyze the data sets with Phragmites australis as outgroup.The phylogenetic trees based on the data set show that the genus Miscauthus(including Triarrhena) formed a monophyletic group.Narenga porphyrocoma was strongly supported to be the sister group of a subclade comprising Miscauthus and Triarrhena.Imperata cylindrica and Saccharum arundinaceum were sister group and formed a subclade,indicating their close affinity.The present authors suggest that Triarrhena should be merged with Miscanthus.The results of phylogenetic analysis also indicate that Saccharum arundinaceum has a closed relationship with Imperata,followed by Narenga and Miscauthus.However it is the most distant to the other species of Saccharum.Since the genera of Saccharum,Narenga and Erianthus are shown to be polyphyletic,further studies on their phylogenetic relationships are still needed.