Objective To construct a recombinant oncolytic virus vvmIL33 that can steadily se-crete mouse IL-33 protein (mIL-33) in targeted tumor cells and to study its synergistic inhibitory effect on tumor. Methods Mouse IL-33 gene sequence was amplified by PCR and inserted into the eukaryotic ex-pression vector pCMS1. The constructed pCMS1-mIL33 was transfected into the parent virus (vJS6)-infected cells by Lipofactamine. Recombinant oncolytic virus vvmIL33 was purified by cell flow sorting. Enzyme-linked immunosorbent assay ( ELISA) was used to detect the level of mIL-33 protein in the culture superna-tant of vvmIL33-infected tumor cells. Recombinant oncolytic virus vvmIL33 and parental virus vJS6 were re-spectively used to infect tumor cells, and then analyzed by plaque formation assay and MTS kit. T cell co-culture experiments were performed to examine the anti-tumor ability of T cells induced by vvmIL33-infected tumor cells. Results Electrophoresis results of the recombinant plasmid pCMS1-mIL33 showed that mIL-33 gene was inserted successfully. Compared with the control group, vvmIL33 could steadily secrete high levels of mIL-33 protein in MC38 cells after infection (P<0. 001). Results of the plaque formation assay showed that vvmIL33-or vJS6-infected CV1 and MC38 cells produced similar amounts of virus at various time points without statistical difference (P>0. 05). Under different multiplicity of infection (MOI), the lytic ability of vvmIL33 against tumor cells was similar to that of vJS6 without statistical difference (P>0. 05). In the T cell co-culture experiments, the concentration of INF-γ protein produced by T cells in the vvmIL33-infected MC38 cell group was significantly increased as compared with that of the vJS6 group (P<0. 05). Moreover, the cytotoxic effect of induced T cells on tumor cells was also significantly increased (P<0. 05). Conclusion The recombinant oncolytic virus vvmIL33 was successfully constructed without damaging its ability to repli-cate and induce tumor cell lysis. Oncolytic virus carrying mIL-33 enhanced the immune effect of T cells and increased anti-tumor effect.