Streptococcus suis serotype 2（SS2）is a zoonosis pathogen and of more and more concern. Suilysin（SLY）is a well-known antigenic virulence factor that secreted by SS2 to the extracellular environments，which has good immunogenicity. In this study，the wild type sly gene and mutant slym gene which has position 463 and 464 mutations were amplified by PCR. Then these genes were inserted into expression plasmids and two E. coli expression systems were constructed respectively. These two systems might express wild type rSLY or rSLYm. The proteins hybrid results showed that rSLY and rSLYm had same molecular weight with the natural wild type SLY. Compared with rSLY，Hemolytic test indicated rSLYm lost its hemolytic ability. Cytotoxicity test with K15，RK13 and SUVEC monolayer cell showed that rSLYm also lost cytotoxicity. Based on mice test，it was failed to prove that rSLYm could induce mouse death. With these Hemolytic test，Cytotoxicity test and animal test，it was demonstrated that mutant rSLYm could be considered as a candidate subunit vaccine antigen of SS2.