Abstract: Objective To explore the components of immunocytes in peripheral blood, lymph gland and cancer tissue of patients with breast cancer. Methods The peripheral blood from 20 healthy volunteers and 40 cases of breast cancer, and cell supension from 18 cases of reactive hyperplasia lymph gland tissue and 40 cases of tumor tissues from patients with breast cancer were collected for detection of the percent of CD₃⁺、CD₄⁺、CD₈⁺、CD₁₉⁺、CD₅₆⁺ cells in their mononuclear cells and the percent of CD_11c⁺CD₁₂₃^-（DC₁）,CD_11c^- CD₁₂₃⁺ （DC₂）cells in their CD₃₄^- Lin^-HLA-DR⁺ cells by flow cytometry. The ratio of CD₄/CD₈ and DC₁/DC₂ was analyzed. Results There was no significant difference between the patients with breast cancer and controls in percent of CD₃⁺,CD₄⁺,CD₈⁺,CD₁₉⁺,CD₅₆⁺ cells and the ratio of CD₄/CD₈ in the peripheral blood （P>0.05）.But the ratio of DC₁/DC₂ in the peripheral blood of patients was markedly lower than that in the controls（P＜0.05）. The percentage of CD₃⁺,CD₄⁺,CD₅₆⁺,CD₁₉⁺ and CD₈⁺ cells was （54.5±6.8）%,（37.8±4.9）%,（13.1±5.5）%,（5.9±3.4）%,（1.9±0.4）% and the ratio of CD₄/CD₈ and DC₁/ DC₂ was 3.6±1.3 and 3.6±1.3 separately in the tissues of reactive hyperplasia lymph glands. The percentage of CD₃⁺,CD₄⁺,CD₅₆⁺, CD₁₉⁺ and CD₈⁺ cells was separately (62.4±17.5)%,(32.0±8.2)%,(26.9±10.5)%,(2.2±2.0)%,(2.3±1.6)%, the ratio of CD₄/CD₈ was 1.3±0.4 and the number of DCs were too less to analyse in the tissue of cancer. Conclusion The components of immunocytes in peripheral blood, lymph gland and cancer tissue of patients with breast cancer showed anti-tumor character, and the decrease in the ratio of DC₁/ DC₂in the circulation may be related to the increase in the number of DC₁ distributing in the drainage lymph gland.