[Aim]  To identify structural characteristics of the Transformer 2 (Tra2) gene, a key gene involved in sex determination in many insects, and quantify its expression in different developmental stages of Calliptamus italicus. [Methods]  Based on the transcriptome database of C. italicus eggs and a comparison of homologous genes in other species, the open reading frame (ORF) sequence fragment of Tra2 was cloned. The predicted structure, multiple sequence alignment and a phylogenetic tree of the cloned sequence were obtained using bioinformatic software. qRT-PCR was used to detect Tra2 expression in eggs, nymphs, and in the testes and ovaries of adult C. italicus. [Results]  The ORF sequence of the Tra2 gene contains 672 bp and encodes 223 amino acids. The protein encoded by Tra2 has an RRM-TRA domain and a unique linker region. A phylogenetic tree indicates that the protein encoded by Tra2 in C. italicus is most closely related to homologous lepidopteran proteins. Tra2 was expressed in different developmental stages of C. italicus but expression was the highest during stage І and Ⅷ of egg development. Tra2 expression was significantly higher in females than in males in both nymphs and adults (P<0.05). [Conclusion]  Tra2 in C. italicus is closely related to homologous genes in other lepidopteran species. Expression in females is significantly higher than in males, suggesting that this gene has greater influence on the development of female than male sexual organs. These results lay a foundation for further elucidating the role of Tra2 in sex determination in C. italicus.