Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have been used as first-line recommended therapy for EGFR mutant non-small cell lung cancer patients. However, epithelial-mesenchymal transition (EMT) can reduce EGFR-TKI sensitivity and lead to resistance. This study was designed to investigate the reversal effect of astragalus polysaccharides (APS) on gefitinib resistance (GR) and to elucidate the underlying mechanisms. PC9 and HCC827 lung cancer cells were stimulated by TGF