Abstract: Objective To investigate the effects of methanol-ethyl acetate partitioned fractions from Descurainia sophia (MEDS) on the proliferation and apoptosis of human non- small cell lung cancer H1975 cells. Methods The systemic solvent extraction method was used to preliminary separation of the effective fractions in the methanol extract of Descurainia sophia. The cytotoxicity of each extract (5, 10, 20, 40, and 80 μg/mL) was tested using MTT assay. Colony cloning method was used to assess the effect of different concentrations of methanol-ethyl acetate partitioned fractions from MEDS (5, 10, 20, 40, and 80 μg/ mL) on the proliferation of H1975 cells. Flow cytometric analysis with Annexin V-FITC/PI staining was performed to detect the apoptosis of the cells after treatment with different concentrations of MEDS fractions (10, 20, and 40 μg/mL). Western blotting was used to evaluate the effects of MEDS fractions on the expressions of apoptosis-related proteins Akt, Bax, and Bcl-2. The anti-tumor activity of 100 mg/kg MEDS fractions was tested in a nude mouse model bearing H1975 cell xenografts. Results MTT assay and colony forming experiment showed that MEDS fractions significantly inhibited the proliferation of H1975 cells in a dose- and time-dependent manner (P<0.05). The results of flow cytometry showed that MEDS fractions induced obvious apoptosis of H1975 cells in a concentration- dependent manner (P<0.05). MEDS fractions also significantly decreased the expressions of Bcl-2 and Akt protein and increased the protein expression of Bax (P<0.05). In the tumor-bearing nude mouse model, MEDS fractions showed potent anti-tumor effects with a low toxicity to affect the body weight and organs of the mice. Conclusion The methanol-ethyl acetate partitioned fractions from MEDS show potent anti-tumor activity both in vivo and in vitro, suggesting their value as promising therapeutic agents against lung cancer.