Abstract: Recently, with the wide application of molecularly targeted therapy in the treatment of non-small cell lung cancer (NSCLC), the average overall survival time of patients who have undergone first line EGFR-tyrosine kinase inhibitor (TKI) treatment can be up to 2 years. But in the process of treatment, even for patients who are highly sensitive to EGFR TKI, drug resistance will eventually emerge at 10 to 12 months after TKI administration. Studies find that the main mechanism of acquired resistant is the secondary mutation of T790M in exon 20 of EGFR. In recent years, detection techniques for T790M mutation as well as treatment strategies for acquired EGFR-TKI resistance caused by T790M mutation update constantly. In this review, we summarize the latest research development about T790M mutation in terms of its mechanisms involved in EGFR-TKI resistance, advanced detection assays and ongoing strategies against the mutation subtype.