Abstract: Cold-inducible DEAD-box RNA helicases are conservative regulator of cold tolerance in archaea, prokaryote and eukaryote. We have got a cold-inducible DEAD-box RNA helicase EST from cold tolerant shrimps. In this study, two cDNA sequence of the DEAD-box RNA helicase gene were obtained by RACR PCR. The two cDNAs were 1430 bp in length including a 139 bp 5'UTR, a 79 bp 3'UTR and a 1212 bp open reading frame, encoding a peptide of 403 aa. Blast analysis showed that the two cDNAs had top hit of DDX homologous, thus named LvDDX5 variant A(LvDDX5A)and LvDDX5 variant B(LvDDX5B). Phylogenetic analysis revealed that LvDDX was related closely to shrimp DDX5,Branchiostoma floridae DDX and Aplysia californica DDX5. LvDDX5A and LvDDX5B were widely expressed, and LvDDX5B was higher in testis, gill, intestine, muscle and ovary, whereas LvDDX5A was higher in hepatopancreas. LvDDX5A but not LvDDX5B was up-regulated in hepatopancreas and heart by cold induction. LvDDX5A can be induced by various low temperatures including 18, 15, 13 and 11 ℃. With different time treatment at 15 and 13 ℃, LvDDX5A increased firstly, reached to the peak at 48h, and decreased afterward. These results suggest that LvDDX5A may play an important role in cold tolerance of Litopenaeus vannamei.