Abstract: Signal transduction and activator of transcription factor (STAT) is an important part of JAK/STAT signaling pathway whose function performs in immunity, growth and development. In this research, the full length cDNA of STAT gene (Lv-STAT) was cloned from hemocytes of Litopenaeus vannamei. Lv-STAT has an 2373 bp ORF encoding 790 aa with a predicted molecular weight of 90.68 kDa and caculated isoelectric point of 5.91. The SMART online software analysis showed that functional domains of Lv-STAT were consisted by four components, STAT_int, STAT- α, STAT- β and SH2 domain. It didn’t have any signal peptide. The key sites of STAT gene family in Lv-STAT are highly conserved. Phylogenetic analysis shows that Lv-STAT is most closely related P. monodon STAT, F. chinensis STAT and human STAT5A and STAT5B. The results of gene expression show that Lv-STAT was mainly expressed in hemocytes and hepatopancreas. The expression profiles of Lv-STAT in hemocytes and hepatopancreas were changed significantly (P<0.01) in the early period after WSSV (White Spot Syndrome Virus) challenging (3 hpi). The result suggests that Lv-STAT might taked part in the antiviral innate immune response of shrimp triggered by WSSV.