Objective To explore the expression of macrophage migration inhibitory factor (MIF) in renal carcinoma tissue and its effect on invasion of renal carcinoma cell.Methods Forty-eight cases of patients definitely diagnosed with renal cancer in the Department of Pathology,the Inner Mongolia Autonomous Region People's Hospital and Baotou Municipal Tumor Hospital from March 2013 to March 2015 served as the research subjects.The expressions of MIF protein and mRNA in renal carcinoma tissues and adjacent normal tissues,renal carcinoma cell lines and normal renal tubular epithelial cells HK-2 were detected by adopting the Western blot and RT-PCR.siRNA MIF and siRNA NC were transfected into renal carcinoma cells by liposome.The transfection effect was detected by Western blot and RT-PCR.The cell viability and invasion ability were measured by MTT and Transwell method respectively.The expression of hypoxia inducible factor 1-alpha (HIF-1α) and matrix metalloproteinase 9 (MMP9) was measured by Western blot.Results The expression levels of MIF protein and mRNA in renal carcinoma tissues were significantly higher than those in adjacent normal tissues (0.89±0.09 vs.0.18±0.02,1.19±0.04 vs.0.19±0.01,P＜0.05).The expression levels of MIF protein and mRNA in renal cancer cell line ACHN,769-p,786-O,Caki-1 cells were higher than those in renal tubular epithelial HK-2 cells (P＜0.05).Compared with the siRNA NC group,the expression levels of MIF protein and mRNA in siRNA MIF group were significantly down-regulated (P＜0.05),the cell viability and invasion ability were reduced (P＜0.05),and the expressions of HIF-1α and MMP9 were down regulated (P＜0.05).Conclusion MIF is highly expressed in renal carcinoma,downregulating MIF expression can significantly inhibit the renal cancer cell invasion,which might be related with inhibiting HIF-1α/MMP9 signaling pathway.