The c2type lysozyme cDNA of Penaeus monodon cloned previously in our lab (GenBank accession no. AF539466) was modified by PCR to delete the signal peptide and subcloned to pBV220 expression vector which contains PRPL promoter to construct the recombinant vector pBV2202lyz. pBV2202lyz was transformed to E. coli DH5αand then induced to express at 42 ℃. A specific band about 16kD in molecular mass was showed by SDS2PAGE analysis , which was larger than those from other species such as human , fish and insects (about 14kD) . The recombinant P. monodon lysozyme existed as inclusion bodies in the cells. The inclusion bodies were collected , washed and then dissolved. And finally the target protein was dialyzed in order to recover its biological activity. Scanned and quantified by the Analysis System of Biology Image showed that the recombinant lysozyme accounted for 32 % of the total cell protein , and was about 90 % after purification. The biological activity of the recombinant protein was evaluated by turbidimetric assay described by Hultmark. The optimum pH and temperature of the lytic activities of the recombinant lysozyme were 6.0 and40 ℃,respectively. The recombinant protein was found to possess potent lytic activities against Micrococcus lysodeikticus12634 , Vibrio alginolyticus As1. 1833 and V. anguillarum E3211. And it has some lytic activities against Edwardsiella tarda E 895205 but with little lytic activities against Aeromonas hydrophila AhG1 , V . parahaemolyticus As1. 1615 and E. coli DH5α. The standard lysozyme (lysozyme from chicken egg white) showed lower lytic activities against Micrococcus lysodeikticus12634 , Vibrio alginolyticus As1. 1833 and V. anguillarum E321 compared with that of the recombinant protein. The present study suggests the potential application of the recombinant P. monodon lysozyme in aqauculture.