The internal transcription spacers (include ITS1,5.8s rDNA and ITS2) of 8 species ofGenus Iris from North China and one outgroup Belamcanda.chinensis were sequenced. Itwas shown that the size of ITS of Iris is from 551bp to 670bp, the length variation was foundboth in ITS1 and ITS2. The length of ITS1 varies from 195bp to 258bp;the length of ITS2 isfrom 192bp to 251bp. The average genetics distance of ITS sequence of Iris is 0.203. Theoverall level of variation and sequence divergence is relatively high compared to otherinfragenetic plant group.In PHYLIP analysis, phylogenetic trees were reconstructed by using NJ method, MLmethod and MP method , and the molecular clock hypothesis was tested. The result supportsthat I.maackii should be a subspecies: I.pseudacorus L.subsp.maackii (Maxim.) M.Z.Sun etY.T.Zhao stat nov. Among the three methods of reconstructing phylogenetic trees by usingITS sequence of Iris, ML method and MP method are easier to get the same result than NJmethod. ITS sequence of Iris rejects the molecular clock hypothesis by likelihood ratio test.
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