is the largest-culturing species of shrimp, which lends to its high economic and natural nutritional value. However, diseases caused by viruses and bacteria often occur in this species, causing huge economic losses to the shrimp farming industry. Since shrimp can only rely on their innate immune system to protect against pathogen invasions, it is important to understand this innate immune system by studying the immune related molecules of shrimp species, such as . This understanding is essential for the prevention and treatment of shrimp diseases. It has been reported that β-thymosins are a class of highly conserved functional peptides that play important regulatory roles in physiological activities such as wound healing, angiogenesis, and antibacterial and antiviral immunity. In this experiment, one β-thymosin gene sequence was successfully cloned from . The full-length cDNA was 1495 bp and the open reading frame (ORF) was 615 bp, which encoded 204 amino acids. It was named because it contained 5 thymosin beta actin-binding motifs (THY). Multiple sequence alignment and phylogenetic tree analysis showed that Penaeus vannamei, and had the highest homology with thymosin β5 of , with a similarity of 77%. Real-time quantitative PCR (qRT-PCR) showed that the gene was expressed in the hepatopancreas, gills, intestine, stomach, muscle and lymphoid organ, and was significantly higher in immune related tissues such as the hepatopancreas and lymphoid organ. The in vitro recombinant protein of Pmβ5 was obtained by a prokaryotic expression technique and the recombinant protein was confirmed to be a Pmβ5 protein by Western Blot analysis. The antibacterial activity of the recombinant protein was further confirmed by the antibacterial experiment (Oxford Cup method). It was found that the recombinant protein had certain antibacterial activity against four bacteria. After 12 hours of inactivation by inactivated was significantly increased, indicating that Pmβ5 may be involved in shrimp resistance to bacterial immunity. In summary, we have found the expression and distribution of and conducted a preliminary study on the function of Pmβ5 in immunity.