, which is an important demersal species in the Yellow Sea and Bohai Sea. Its production ranks only second to that of in China. This species is mainly charactered by its tender meat, high reproduction, fast growth and adaption to a wide range of environment. Recently, the aquaculture area has been expanded gradually, but under the condition of centralization-breeding factor, the shrimp is easy in stressing conditions, which may cause diseases even death. In this study, we isolated the cDNA sequence of serine protease inhibitors (serpin) gene from using RT-PCR and RACE methods. The full-length cDNA of the serine protease consisted of 1 516 bp with a 1 245 bp open reading frame (ORF), encoding 414 amino acids. The predicted molecular mass of serine protease protein was 45.06 kD, and the theoretical isoelectric point was 5.694. The serine protease protein sequence contained two glycosyl binding sites, which had 49% homology. Tissue expression analysis suggested that serpin mRNA expression was highest in the hemocytes and lowest in the muscle. Real time-PCR analysis revealed that the expression of serpin gene was significantly higher in hemolymph 8 h after salinity exposure compared to the control group. Furthermore, the serpin gene expression in the hepatopancreas exhibited two obvious peaks at 2 h and 24 h after salinity stress compared with the control group. Our results suggest that serpin gene plays an important role in the salinity stress response of .