Abstract:Abstract: The genetic relationship and evolutionary system of Schizonepeta tenuifolia from 5 different producing areas in China were analyzed based on the ribosome ITS1 and ITS2 sequences.Their complete ITS and 5.8S sequences on the ribosome region were amplified by PCR and were analyzed by software Clustal X(2.0) Multiple Sequence Alignments and Neighbor Joining.ITS sequence of S. tenuifolia from Hebei Province representing Chinese S. tenuifolia was compared with those from United States, Japan and Korea to construct phylogenetic tree. The results showed G/C contents of ITS1 and ITS2 sequences of S. tenuifolia from 5 different producing areas were high.ITS length was all 749bp for S. tenuifolia from 5 different producing areas with the same ITS sequence. Lengths of ITS1, 5.8S and ITS2 were 231bp, 168bp and 236bp respectively. The ITS sequence similarity was 100% among S. tenuifolia from China, Japan and Korea; and 99% between those from China and America. Compared with S. tenuifolia from America, S. tenuifolia from China had 7 bases mutation. On the base of ITS sequence data, S. tenuifolia from different counties constructed a monophyletic group with 2 branches, one was consisted of S. tenuifolia from China, Japan and Korea, the other one was only consisted of that from America. ITS sequence similarity suggested that S. tenuifolia from 5 different producing areas belonged to one species.