Sequences from a region of the nuclear ribosomal 18S rDNA gene of approximately 1 912 base pairs （bp） were used to generate a molecular phylogeny for the Pentatomomorpha based on 53 species representing 21 putative families. Phylogenetic analyses using the most parsimony method （MP）, maximum likelihood method （ML）, and neighbor joining method （NJ） showed strong support that the Pentatomomorpha lineage is a monophyly and the superfamily Aradoidea is a sister group to the remainder of the Pentatomomorpha （Trichophora）. The Trichophora could be divided into two clades ： one clade consisted of the monophyletic superfamilies Pentatomoidea and Pyrrhocoroidea; the other was mainly the polyphyletic superfamilies Lygaeoidea, Coreoidea and Idiostoloidea. The superfamilies Lygaeoidea and Coreoidea were both polyphyletic. Within Lygaeoidea, Piesmatidae was sister to Berytidae. They formed a clade locating at the basal of the Trichophora and distantly related to the other two families Lygaeidae and Rhyparochromidae. This research suggested that 18S rDNA was a proper marker to reconstruct the phylogeny of Pentatomomorpha that was accordant to morphological studies and the research of Li et al （2005）. The Pyrrhocoroidea was further divided from the Coreoidea （s./at ）. It was suggested that the Piesmatidae might be assigned as a superfamily of Pentatomomorpha rather than a family in Lygaeoidea.
