Objective To observe the post-operative variation of immune function in patients with renal cell carcinoma and to investigate the significance of diagnosis and therapeutic effect evaluation by detecting the T-lymphocyte subset level in the peripheral blood of patients with renal cell carcinoma.Methods Thirty-nine patients with renal cell carcinoma were recruited between 2006 and 2009. The level of CD3+,CD4+,CD8+,and CD4+/CD8+ in the peripheral blood of these patients was detected by flow cytometry before and after operation and compared with that in control group. Results The level of CD3+、CD4+ and CD4+/CD8+ in patients with renal cell carcinoma was lower than in control group while the post-operative level of CD3+、CD4+ and CD4+/CD8+ was significantly higher. Conclusions The pre-operative immune function in patients with renal cell carcinoma is inhibited to some extent.Detecting the T-lymphocyte subsets level in the peripheral blood of patients with renal cell carcinoma is of positive clinical significance for evaluation of the cell immue status, diagnosis of the disease and observation of the therapeutic effect.