Although more and more drugs had been proved to be effective in controlling tumor cells, lung cancer was still the leading cause of cancer-related deaths all over the world. This study aimed to investigate the effect and mechanism of puerarin on the invasion and metastasis of A549 lung cancer cell line.A medium containing puerarin was prepared according to the gradient concentration, and 10, 20, and 40 µmol/L were selected as the experimental group (low, medium, and high concentration groups, respectively) according to the cytotoxicity experiment. Meanwhile, 0 µmol/L was used as the control group.Following administration, metastasis-related indexes were detected by the cell scratch test, cell migration test, gene difference detection, and western blotting. 24 hours after administration, the cell scratch and Transwell showed that the migration ability of A549 cells decreased with the increasing puerarin concentration. The polymerase chain reaction (PCR) and western blotting results demonstrated that the expression of the cell invasion and metastasis-related factor, matrix metallopeptidase 9 (MMP9), was negatively correlated with drug concentration. Further investigation demonstrated that the phosphorylation of extracellular signal-regulated kinase (ERK) was also inhibited.Puerarin can inhibit the expression of invasion and metastasis-related factors by inhibiting the phosphorylation of ERK.