Objectives Objectives To investigate how the imbalance of innate lymphoid cells (ILCs)in the peripheral blood of patients with lung adenocarcinoma affects the balance of downstream mononuclear macrophages and T helper (Th) cells, and to identify the impact of the imbalance of ILCs on the immune status and prognosis of lung adenocarcinoma. Methods The peripheral blood of 20 patients with lung adenocarcinoma and normal controls were collected. The percentage of ILCs, mononuclear macrophages and T lymphocyte in peripheral blood were analyzed by flow cytometry. The characteristic cytokine secretion levels of various types of immune cells in peripheral blood were detected by real-time fluorescence quantitative PCR. Results Compared with the normal controls, the proportion of M2 mononuclear macrophages, ILC1 and ILC2 in patients with lung adenocarcinoma was up-regulated, while the proportion of M1 mononuclear macrophages, CD4+ T and CD8+ T was down-regulated. The mRNA expression of related cytokines of M1 mononuclear macrophages and ILC1 were decreased; while the mRNA expression of related cytokines of M2 mononuclear macrophages and ILC2 were increased. Along with the decreased CD4+T cells-associated cytokine T-bet mRNA expression, and the increased GATA3 mRNA expression. Moreover, the expression of PD-1 in CD8+ T cells was also up-regulated. Conclusion The imbalance of ILCs in peripheral blood of patients with lung adenocarcinoma promotes the imbalance of mononuclear macrophages and Th cells, which altogether maintains the immunosuppression in patients with lung adenocarcinoma, and promotes the development of lung adenocarcinoma.