To investigate the effect of Tanreqing injection on immune activity of peripheral blood lymphocytes of patients with lung cancer. The peripheral blood lymphocytes of patients with lung cancer and healthy persons were separated by the density gradient centrifugation method for subsequent experiments, with those from healthy persons as the positive control. The effect of Tanreqing injection on stimulating the proliferation of lymphocytes with phytohemagglutinin (PHA) was determined by MTT method. The effect of Tanreqing injection on the lymphocyte secretions of IFN-γ and TNF-α and the subset ratio of lymphocytes cultured separately or with Tanreqing injection of different concentrations were examined by ELISA and flow cytometry (FCM) respectively. In addition, the LDH release assay was used to detect the cytotoxicity of cytotoxic T cells (CTL) and natural killer cells (NK). According to the findings, all of immunological indexes of lymphocytes from patients with lung cancer were weaker than that of healthy persons, but with the obvious increases in proliferation activity and IFN-γ and TNF-α secretions of lymphocytes co-cultured with Tanreqing Injection (P < 0.05). Among lymphocyte subsets co-cultured with Tanreqing Injection, CD3+, CD3+ CD4+ and CD3- CD16 + 56+ cell ratios notably increased, whereas CD4+ CD25+ Treg cell ratio obviously decreased (P < 0.05). In the meantime, Tanreqing injection can markedly promote the cytotoxicities of CTL and NK (P < 0.05). In conclusion, Tanreqing injection shows a significant effect in promoting the immune activity of lymphocytes from patients with lung cancer and their anti-tumor immunity.