Hsp90 is an ubiquitous molecular chaperone protein, which plays an important role in regulating maturation and stabilization of many oncogenic proteins. Due to its potential to simultaneously disable multiple signaling pathways, Hsp90 represents great promise as a therapeutic target of cancer. In this study, we synthesized flavokawain analogues and evaluated their biological activities against drug-resistant cancer cells. The study indicated that compound 1i impaired the growth of gefitinib-resistant non-small cell lung cancer (H1975), down-regulated the expression of Hsp90 client proteins including EGFR, Her2, Met, Akt and Cdk4, and upregulated the expression of Hsp70. The result strongly suggested that compound 1i inhibited the proliferation of cancer cells through Hsp90 inhibition. Overall, compound 1i could serve as a potential lead compound to overcome the drug resistance in cancer chemotherapy.