Objective：To establish an osimertinib-resistant non-small cell lung cancer cell line H1975AR，identify parental and drug-resistant cells，and explore the mechanism of drug resistance. Methods：Induction of H1975 by increasing the concentration of osimertinib in vitro was performed to establish osimertinib-resistant cell line H1975AR. The morphological differences between the two cells were compared by light microscopy and Giemsa staining. Next generation sequencing（NGS）was used to detect epidermal growth factor receptor（EGFR）mutations. Cell proliferation was determined by SRB assay to access sensitivity to EGFR-tyrosine kinase inhibitor（TKI） and chemotherapeutic drugs. Western blot detected the changes of EGFR and downstream proliferation signaling pathway after treating with 0、10、100、 1 000 nmol/L osimertinib for 6 h. Results：①The resistance index of H1975AR measured by SRB assay was 3 634.75，which indicated that H1975AR was an osimertinib-resistant cell line. ②The morphology of drug-resistant cell line changed and the nuclear-to-cytoplasmic ratio increased. ③Compared with H1975，the inhibitory effected on p-EGFR and p-ERK in H1975AR were not obvious，and the same dose concentration had a weak inhibitory effect on p-AKT in H1975AR，and the expression of c-Met was down-regulated. ④H1975 and H1975AR were resistant to the first-generation EGFR-TKI and sensitive to cisplatin and paclitaxel. Conclusion：The EGFR mutation of cis-C797S in H1975AR cells is the main mechanism of osimertinib resistance and H1975AR is sensitive to cisplatin and paclitaxel.