Objective To observe the expression levels of Farnesoid X receptor (FXR) in non-small cell lung cancer (NSCLC) tissue and cell lines, and to explore whether the role of FXR in the proliferation and invasion of NSCLC cells is related to the regulation of miR-21. Methods From 2010 to 2012, 80 cases of NSCLC tissue and matched normal tissue were collected. The expression of FXR in the NSCLC tissue and cell lines was analyzed using immunohistochemistry or Western blot. The effects of GW3965 (1 ~ 5 μmol / L) on cell viability and invasion and miR-21 levels were evaluated using CCK-8, transwell and qRT-PCR. MiR-21 was overexpressed or knocked down using transfection technology, and the effects on cell viability and invasion were evaluated. Moreover, the relationship between FXR and miR-21 was analyzed by double luciferase assay. Results Compared with the adjacent non-tumor normal tissue, the expression of FXR was significantly lower in NSCLC tissue (P<0. 001). Kaplan-Meier analysis revealed that low FXR expression predicted a worse prognosis for NSCLC patients (χ²= 4. 496, P= 0. 033). There were significant differences in clinical stage, tumor size, T stage and lymph node metastasis (N stage) between high- and low-FXR tumors ( P< 0. 05). GW3965 promoted FXR protein expression in A549 cells in a dose-dependent manner, inhibited cell proliferation and invasion and decreased miR- 21 expression. Overexpression of miR-21 significantly reversed the inhibitory effects of FXR on the growth and invasion of NSCLC cells (P< 0. 05), and miR-21 silencing significantly enhanced the inhibitory effects of FXR on the growth and invasion of NSCLC cells (P<0. 05). The double luciferase assay confirmed that FXR inhibited the proliferation and invasion of NSCLC cells by targeting miR-21. Spearman’ s test revealed a strong negative correlation between FXR and miR-21 expression in NSCLC specimens (P< 0. 001). Furthermore, Kaplan-Meier analysis revealed that a coexistence pattern of “FXR low” and “miR-21 high” predicted the worst prognosis in NSCLC patients (χ²= 8. 201, P= 0. 004). Conclusions FXR inhibits the growth of NSCLC cells by downregulating miR-21, suggesting that regulation of FXR/ miR-21 may be a potential strategy for the treatment of NSCLC.