Abstract: Objective: To investigate the mucin 1(MUC1) expression in renal clear cell carcinoma and its clinical significance.Methods: The MUC1 expressions of renal clear cell carcinoma(RCCC) tissue in 57 cases(RCCC group) and paracancerous tissue in 21 cases(paracancerous group) were detected by immunohistochemical method.The average optical density(OD) value in positive staining area was measured by Image-Pro Plus 6.0 analysis software.Results: The MUC1 expressions in cytoplasm of renal cancer cells and paracancerous tissue were found.The average OD value in RCCC group and paracancerous group were 0.429 5±0.093 9 and 0.337 1±0.082 2,respectively,the difference of which was statistical significance(P<0.01).The MUC1 expression was correlated with the clinical stage and metastasis of RCCC(P<0.01 and P<0.05).Conclusions: The high level expression of MUC1 may play important roles on the occurrence,progression,invasion and metastasis in RCCC,which may be a target antigen in the immunotherapy of renal carcinoma.