Abstract: Serine proteinase inhibitors (SPI) play an important role in regulating humoral immune by controlling the activity of serine proteinase (SP) in the process of protease cascade. Serpin family members participate in numerous biological processes by regulating the activity of serine and cysteine proteinases, such as blood clotting, complement activation, fibrinolysis function, inflammation, tumor suppressor and hormone transfer process. In our previous research, we cloned a serpin-type serine proteinase inhibitiorSPI gene was cloned from hemocytes of Chinese shrimp (Fc-serpin, GenBank accession number: DQ318857). The transcript of Fc-serpin was induced in response to the infection of bacteria and white spot syndrome virus (WSSV). In this research, recombinant Fc-serpin (rFc-serpin) was successfully expressed in bacteria E.coli and purified for further research of bioactivity. The concentrations of purified target proteins were 0.3g/L. rFc-serpin showed in vitro antimicrobial activity against main pathogens including Gram-positive, Gram-negative bacteria and fungi.These results suggests that rFc-serpin might play a crucial role in the innate immunity of the shrimp and is expecting to be applied in disease control.