Abstract: Objective: To analyze the effect of Argon-Helium cryosurgery (AHCS) on CD 4 + CD25+ regulatory T cells (Treg) and its implication in patients with advanced renal carcinoma. Methods:,Peripheral venous blood samples were ob -tained from 32patients with advanced renal cell carcinoma before and after AHCS. The proportions of Treg cells and T lym -phocyte subsets (CD3 + T, CD4 + T, CD8 + T, CD4 + T/CD8 + T, and NK cells) in the peripheral blood were measured by flow cytometry. Enhanced CT or enhanced MRI was used to observe the necrosis of tumor at1 month after AHCS. The areas with no imaging enhancement in tumor were regarded as tumor necrosis. The necrosis rate was measured by Cavalieri method and the tumor burden was evaluated.Results:At 3 months after AHCS, the percentages of Treg cells were gradual-ly decreased from 4.18%±1.58% to1.96%±0.54%, with a significant difference (P=0.001 ). At 3 months after AHCS, the pro-portions of CD 3 + T, CD4 + T, NK and CD4 + T/CD8 + T were gradually increased from 19.26 ±7.52%,43.54%±12.99%, 1.15%±0.57%, and17.49%±8.36% to30.83%±5.69%,49.58± 10.76%,1.84%±0.12%, and27.63%±8.20%, with a statistical significance ( P=0.000 , P=0.003 , P=0.02, and P=0.001 ). The proportion of CD 8 + T was decreased from 40.86%±8.89% to the lowest ratio ( 26.74 ±4.29%) at3 months after AHCS, with a significant difference ( P=0.000 ). At 3~6 months after cryo-therapy, there was only a slight change in the proportions of CD 3 + T, CD4 + T, CD4 + T/CD8 + T, NK, CD8 + T, and Treg cells, with no significant difference ( P>0.05). Correlation analysis showed that the decrease in tumor burden was positively correlated with the decrease of the proportion of Treg cells (r=0.793 , P<0.01). Conclusion:After AHCS, the distribution of T-lymphocyte subsets can be improved and the anti-tumor immune response was strengthened. The percentage of Treg cells is correlated with tumor burden.