Telomerase has the function of maintaining telomere length, and its catalytic subunit TERT (Telomerase Reverse Transcriptase) is tightly regulated in higher organisms such as mammals, and is usually not expressed in somatic cells. However, in lower eukaryotes such as invertebrates, TERT is often expressed in somatic cells, but the physiological function is not clear. In order to clarify the physiological function of TERT, the TERT gene of Lipaphis erysimi (Kaltenbach) was cloned and analyzed for its spatial and temporal expression. The results showed that the CDS region of the radish TERT gene was 2658 bp and capable of encoding 885 amino acids. Its secondary structure contained 41 α-helices and 60 coiled coils. Phylogenetic analysis indicated that the Lipaphis erysimi TERT gene has the closest relationship with Diuraphis noxia, and has high homology with Myzus persicae and Acyrthosiphon pisum, but has low homology with other insects. Real-time quantitative PCR showed that the TERT gene was expressed in all ages and tissues during the growth and development of Lipaphis erysimi,and the relative expression of adult TERT gene was higher than that of 1st, 2nd, 3rd and 4th nymphs. The expression of TERT gene in the abdomen of the Lipaphis erysimi was the highest, followed by the head, and the lowest in the chest, but lower than the expression of the whole worm. This study laid the foundation for further study of the physiological functions of TERT in insects.