Objective To investigate the effect of calycosin on proliferation and apoptosis of lung adenocarcinoma cells line SPC-A1 in vitro. Methods After treatment with different concentrations of calycosin (25, 50 and 100?μg/ml) for different time (12, 24, 36 and 48?h), the proliferation of lung adenocarcinoma SPC-A1cells were detected by MMT assay; Hoechst33258 fluorescent staining was employed to observe the nucleus; the cells apoptosis were detected by flow cytometry; Western blot and real-time PCR experiment were used to analyze the expression of calycosin levels of Cyclin D1, CDK4, CDK6 protein and mRNA in SPC-A1 cells with (25, 50 and 100 μg/ml) calycosin for 48?h. Results MTT experiment showed that the cell proliferation of SPC-A1 cells was inhibited by calycosin, and in a dose-dependent and time-dependent manner (P?