Dry rhizome of Dryopteris crassirhizoma Nakai (Dryopteridaceae), also known as Guan Zhong, is a traditional Chinese herbal medicine used in the treatment of viral disease. But the dry rhizomes of Woodwardia JAPONICA (L. f.) Sm., OSMUNDA JAPONICA Thunb. and Cyrtomium fortunei J. Sm. are also used as Guan Zhong in local areas. The adulterants are similar to Dryopteris crassirhizoma. It is difficult to identify the botanical origin of these herbs. In our study, sequences of the cpDNA RBCL gene were determined and analyzed for Dryopteris crassirhizoma and adulterant species, where nineteen molecular markers had been determined. Also, amino acid sequences translated from the RBCL gene were analyzed and four important molecular markers were detected. Based on cpDNA RBCL and translated amino acid sequences, Dryopteris crassirhizoma can easily be distinguished from the other three fern species.