| Tettigonioidea is the second biggest superfamily in Ensifera of Othoptera. More than 6000 species have been described which are belong to 1070 genera in worldwide. Most of them are phytophagous insects and important pests in agriculture and forest; others are predatory insects and are insect enemy and potential resources for biocontrol. Some katydids are big size and abundance in nutrition which can be used as edible resources. Spermatophores is a sperm-free mass that is eaten by the female after copulation. It is a very costly male investment that influences sexual selection and the courtship roles of the sexes. Thus katydids are useful material for ethology. The systematics study of them has not only theoretical but also practical value in pests control, plant protection, and resources usage. There have comprehensive studies of taxonomy, cell biology, biochemistry, ethology, acoustical mechanism and other aspects on Tettigonioidea home and abroad. Currently, however, the molecular systematic research on katydids insects is still very limited. The abroad disputes of ordinal classification and phylogeny have even existing in all times. There is no classification admitted by most systematists in worldwide.The genomic DNA were extracted from 48 species of katydids among them 46 species belong to Tettigonioidea for ingroup and 2 species belong to Gryllacridoidea for outgroup. 47 sequences of Cyt b (579bp) and 24 sequence of 28S rDNA (420-423bp) have been acquired by PCR amplification and sequenced using specific two pare primers. The base frequency, amino acid frequency, base substitution and genetic distance of DNA sequence have been analyzed by using some biosoftware such as ClustalX1.81, MEGA 2.0. Phylogenetic signal have been tested via base substitution saturation analysis, g1 and PTP tests. Results show there are stronger phylogenetic signal in the data sets. We adopted Cyt b, 28S rDNA gene sequences and their conbined data set as molecular marker and reconstructed the phylogenetic relationships through NJ, MP, ML and BI in PAUP~* 4.0 b10(PPC), MrBayes V3.0, TreeRot.We conducted ILD and PBS tests on combined data set and carried out KH and SH test on 4 molecular trees inferred from Cyt b data set and combined data set in PAUP~* 4.0 b10(PPC) and TreeRot, according to results of tests, consensus tree of 3phylogenetic trees were made. Summarizing the outcomes, we can conclude the results as follows:1. The average content of T, C, A, G of Cyt b gene sequence of 45 species of Tettigonioidea are 37.6%, 21.4% 29.4% and 11.5% respectively, and A+T content is 67%, G+C content is 23%, which shows a strong A+T bias. The Cyt b gene sequence of all insects codes 193 amino acids. 43 species contain 19 amino acids only and Isopsera dentculata and Anisotima dispar contain additional Cys. The contents of Leu, Ile and Phe are the highest in all species.The average content of T, C, A, G of 28S rDNA gene sequence of 22 species of Tettigonioidea are 21.4%, 27.4% 17.7% and 33.5% respectively, and G+C content is 60.9%, G+C content is higher than A+T content obviously, which shows a strong G+C bias.2. The average transition and transversion ratio of Cyt b gene sequence is 1.2. Transition is lightly more than transversion. Substitution saturation main takes place on the third position of codon. Transition frequently occurs between T and C and transversion usually occurs between T and A in total data set. Substitution on the third position is the most frequent (67.9%).The average transition and transvertion ratio of 28S rDNA gene sequence is 1.5, transition is obviously more than transversion, Transition frequently occurs between T and C and transversion usually occurs between T and G. Substitution saturation ananlysis shows the sequence is conservative.3. The average uncorrected distance of Cyt b gene is 0.18. Most of them vary from 0.1 to 0.3. The average uncorrected distance of 28S rDNA vary between 0 and 0.08; seven pare distance is zero.4. x~2, g1 and PTP tests were conducted on Cyt b data set and its subdata sets, 28S rDNA data set, combined data set. Results show that there exist stronger phylogenetic signal.5. phylogenetic relationship were reconstructed based on Cyt b data set of 45 species kdtidids, 28S rDNA data set of 22 species and combined data set of 21 species. Four trees both of Cyt b data set and combined data set were tested by KH and SH based on likelihood, the likelihood value of MPT and MLT are smallest respectively. P-values are less than 0.05 of 2 NJT after testing, thus consensus trees were constructed from MPT, MLT and BIT for Cyt b data set and combined data set.6. The terminal branch of consensus tree of Cyt b data set resolved well which...
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