Objective In this study, we observed the effects of IL-33 on tumor immune response in lung cancer-bearing mice using wild type and MyD88(-/-) mice respectively. Methods Wild C57BL/6 (C57BL/6WT), MyD88 knockout C57BL/6 mice (C57BL/6 MyD88(-/-)) and Lewis cells were used in this study. Cell proliferation, cytokine release and cytotoxicity were detected. Results IL-33 could significantly up-regulate specific cellular immunity, inhibit tumor growth and improve survival time in wild type mice group, and it had dose dependent effect. However, IL-33 had no effect on cell immunity and tumor growth in MyD88(-/-) mice group. Compared with MyD88(-/-) mice, IL-33 could significantly increase the ratio of CD8+T cells to neutrophils in wild type mice, while the percentage of tumor infiltrating CD11b+ cells, Mo-MDSC, F4/80+ macrophages and mDC cells decreased significantly in wild type mice group. IL-33 could upregulate the expression of CD107a and IFN-gamma in CD8+T cells and NK cells of wild type mice, while IL-33 could not upregulate them in MyD88(-/-) mice. IL-33 could upregulate the expression of CD40, CD80, CD86 and CD205 in DC cells in wild type mice, induce T cells to differentiate into Th1 cells and enhance tumor cell immunity. Conclusions IL-33 could promote differentiation and maturation of DC cells through MyD88 pathway, up-regulate the tumor immunity of CD8+T cells and NK cells, and inhibit the proliferation of lung cancer cells.