Objective: To investigate the role of estrogen receptor in epithelial mesenchymal transition (EMT) of lung adenocarcinoma cell line A549. Methods: Estrogen receptor antagonists were used to inhibit estrogen receptor in A549 cell line, and then estrogen of 1× 10-8 mol/L concentration was used to stimulate the cell lines before and after inhibition. The expression of EMT markers in each group was detected by q-RT-PCR and Western blot, and the cell migration rate of each group was detected by Transwell, and the statistical difference between each group was calculated. Results: The mRNA expression of vimentin in estrogen group was 5.81± 0.71, which was significantly higher than that in blank control group. The mRNA expression of E-cadherin in estrogen group was 0.43± 0.07, which was significantly lower than that in blank control group. The number of cell migration in estrogen group was 80.17± 8.82, which was significantly higher than that incontrol group. The mRNA expression of vimentin were 7.63± 0.92 and 6.29± 0.73 before and after treatment with MPP, which were significantly higher than those in control group (P<0.05); the mRNA expression levels of E-cadherin were 0.39± 0.05 and 0.42± 0.06, which were significantly lower than those in the control group; the number of cell migration were 85.21± 11.56 and 78.69± 9.63 before and after treatment with MPP, which were significantly higher than that of the control group, and there was statistical difference between the two groups. The mRNA expression of vimentin was 1.21± 0.15 and 1.17± 0.13, the mRNA expression of E-cadherin was 0.86± 0.12 and 0.93± 0.11, and the number of cell migration was 39.85± 5.22 and 37.21 ± 4.95 in estrogen plus PHTPP group and estrogen plus MPP and PHTPP group respectively which were no significant difference with control group. The trend of EMT marker protein expression and mRNA expression in each group was the same. Conclusion: Estrogen receptor β is an important target for estrogen to promote the EMT process of A549 cell line. It plays an important role in the carcinogenesis and development of lung adenocarcinoma, and can be used as the research direction of further targeted therapy. [ABSTRACT FROM AUTHOR]