ObjectiveTo explore the intervention effect and molecular mechanism of Dabufei decoction in Dunhuang formula combined with cisplatin on Lewis lung adenocarcinoma-bearing mice. MethodFifty C57BL/6J mice were used， with 10 randomly assigned to the blank group （without modeling）， and 40 subcutaneously inoculated with Lewis cells to establish a Lewis lung adenocarcinoma-bearing mouse model. These 40 mice were randomly divided into the following four groups （with 10 mice in each group）： Model group （equal volume of physiological saline）， cisplatin group （5 mg·kg^-1）， Dabufei decoction group （14.35 g·kg^-1·d^-1）， and Dabufei decoction combined with cisplatin group （Dabufei decoction 14.35 g·kg^-1·d^-1 + cisplatin 5 mg·kg^-1）. Each group was treated continuously for 14 days. The general condition of the mice was observed， body weight changes were recorded， and the tumor inhibition rate， spleen index， and thymus index were calculated. Peripheral blood white blood cell （WBC）， platelet （PLT）， and hemoglobin （HGB） were detected by routine blood tests. Flow cytometry was used to detect the expression of CD4⁺CD25⁺FoxP3⁺ regulatory T cells （Treg） and natural killer （NK） cells in the spleen. Western blot and real-time quantitative polymerase chain reaction （Real-time PCR） were used to determine the expression of proteins and mRNA related to the phosphatidylinositol 3-kinase （PI3K）/protein kinase B （Akt）/mammalian target of rapamycin （mTOR） signaling pathway in tumor tissues. ResultCompared with the blank group， the model group showed decreased body weight （P<0.05）， spleen index， and thymus index （P<0.05）， decreased percentage of NK cells in the spleen （P<0.05）， increased percentage of Treg cells （P<0.05）， and decreased counts of WBC， PLT， and HGB （P<0.05）. Compared with the model group， the Dabufei decoction group exhibited significant tumor growth inhibition， increased body weight， and reduced tumor weight （P<0.05）， increased percentage of NK cells （P<0.05）， decreased proportion of Treg cells （P<0.05）， and increased counts of WBC， PLT， and HGB （P<0.05）. In the cisplatin group， tumor growth was significantly inhibited， body weight significantly decreased （P<0.05）， and tumor weight significantly reduced （P<0.05）. The spleen index and thymus index decreased （P<0.05）， and the percentage of Treg cells significantly decreased （P<0.05）. The counts of WBC， PLT， and HGB significantly decreased （P<0.05）. In the Dabufei decoction combined with cisplatin group， tumor growth was significantly inhibited， and tumor weight significantly reduced （P<0.05）. The levels of phosphorylated PI3K， Akt， and mTOR proteins and mRNA in tumor tissues were significantly reduced in all medication groups （P<0.05）. Compared with the cisplatin group， the Dabufei decoction combined with cisplatin group showed significantly inhibited tumor growth， reduced tumor weight （P<0.05）， increased body weight （P<0.05）， increased spleen index and thymus index （P<0.05）， increased percentage of NK cells （P<0.05）， decreased percentage of Treg cells （P<0.05）， significantly increased counts of WBC， PLT， and HGB （P<0.05）， and reduced levels of phosphorylated PI3K， Akt， and mTOR and their mRNA （P<0.05）. ConclusionDabufei decoction combined with cisplatin has a synergistic effect with reduced toxicity， effectively regulating immune function， increasing the proportion of NK cells， reducing the proportion of Treg cells， improving bone marrow suppression， and downregulating the PI3K/Akt/mTOR signaling pathway to inhibit tumor growth in Lewis lung adenocarcinoma-bearing mice.