Objective：To detect the expression of interleukin(IL)-33 in renal cell carcinoma(RCC) and its effect on invasion of human 786-0 cells.Methods：IL-33 protein in 34 patients with different grades of RCC tissues and para-adjacent tissues was detected with immunohistochemistry assay.Transwell invasion assay was used to investigate the effect of IL-33 on invasion of 786-0 cells.Western blot assay was conducted to detect the markers of epithelial-mesenchymal transition(EMT) in 786-0 cells after IL-33 treatment.Results：IL-33 protein expression was significantly higher in RCC tissues compared to para-adjacent renal tissues(P＜0.001).IL-33 enhanced 786-0 cells invasion in vitro.Moreover，the expression of E-cadherin was significantly decreased while the expression of vimentin was significantly increased after IL-33 treatment.Conclusion：IL-33 is overexpressed in RCC tissues and may contribute to renal cancer cells invasion by inducing EMT.