The complete sequences of mitochondrial DNA (mtDNA) from the three new grasshopper species, Euchorthippus fusigeniculatus, Mekongiana xiangchengensis and Mekongiella xizangensis, consisting of 15772 bp, 15567 bp, and 15885 bp, respectively, were analyzed and compared to mtDNAs from other 19 Orthoptera species obtained from GenBank. The three mitochondrial genomes contain a standard set of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes. and an A T-rich region in the same order as those of the other analyzed caeliferan species, but different from those of the ensiferan species by the rearrangement of trnD and trnK. The putative initiation codon for the cox1 gene is ATC in E. fusigeniculatus, CTG in M. xiangchengensis and CCG in M. xizangensis. All secondary structures of tRNA-Ser^(AGN) in the three species lack a DHU arm. In this study, we stressed the comparative analysis of the stem-loop secondary structure in A T-rich region of all Orthoptera species available to date, and report new findings which may facilitate further investigation and better understanding of this secondary structure. Finally, we undertook a phylogenetic study of all Orthoptera species available from GenBank to date based on three different datasets using parsimony, maximum likelihood, and Bayesian inference. Our result showed that protein-coding genes (PCG) and amino acid sequences (PCG_PROT) provided good resolution of higher-level relationships within the Orthoptera, whereas ribosomal RNA genes (RIBO) perform poorly under different optimality criteria.