Objective To investigate the effects of breviscapine on the proliferation and radiosensitivity of human non-small cell lung cancer (NSCLC) A549 cells. Methods A549 cells in the logarithmic growth phase were treated with serial concentrations (0, 2, 4, 8, 16, 32 μmol·L?1) of breviscapine for 48 h. The cell proliferation inhibition rate was measured using the MTT assay, and the half-maximal inhibitory concentration (IC??) was calculated and used as the breviscapine concentration in subsequent experiments. A549 cells were treated with serial radiation doses (0, 1, 2, 4, 6, 8 Gy) alone or in combination with breviscapine (14.75 μmol·L?1), and the mean lethal dose (D?) and sensitization enhancement ratio (SER) were calculated. The cells were divided into four groups: control, breviscapine alone, radiotherapy alone, and breviscapine combined with radiotherapy. The MTT assay was used to detect cell proliferation inhibition, flow cytometry to assess apoptosis, GFP-LC3 plasmid transfection to observe autophagy, and Western blotting to measure the expression of apoptosis- and autophagy-related proteins.Results The IC?? of breviscapine for A549 cells was (14.75±1.82) μmol·L?1. The D? values for the radiotherapy alone group and the combination group were (2.19±0.15) Gy and (1.64±0.10) Gy, respectively, with an SER of 1.34. The breviscapine alone, radiotherapy alone, and combination of breviscapine with radiotherapy significantly increased the proliferation inhibition rate, apoptosis rate, number of autophagosomes, relative expression levels of Bax, Cleaved Caspase-3, Beclin1, and LC3-Ⅱ proteins, as well as the ratios of Bax/Bcl-2, Cleaved Caspase-3/Caspase-3, and LC3-Ⅱ/LC3-Ⅰ, while significantly decreasing Bcl-2 expression (P<0.05). The effects in the combination group were significantly stronger than those in the breviscapine alone or radiotherapy alone groups (P<0.05).Conclusion Breviscapine can inhibit the proliferation of A549 cells and enhance their radiosensitivity by regulating the expression of related proteins to promote apoptosis and autophagy, providing new insights for the treatment of NSCLC.