Objective: To investigate the effects of Krüppel-like factor 4 (KLF 4) knockdown on epithelialmesenchymal transition (EMT), cell migration and invasion of prostate cancer cells. Methods: The prostate cancer cells with stable knockdown of KLF 4 named as LNCaP-shKLF4 cells and the LNCaP-con cells as the control were constructed. The expressions of KLF4 mRNA and protein in LNCaP-con and LNCaP-shKLF4 cells, and the expressions of EMTassociated gene mRNA and protein in the prostate cancer PC3-shKLF4 cells with stable knockdown of KLF 4 and the PC3-con cells (as the control) as well as the LNCaP-shKLF4 and LNCaP-con cells were detected by real-time fluorescence quantitative-PCR and Western blotting, respectively. The abilities of migration and invasion of PC3-shKLF4 and PC3-con cells as well as LNCaP-shKLF4 and LNCaP-con cells were detected by Transwell chamber assay. Results: LNCaP-shKLF4 and LNCaP-con cells were successfully constructed. The expression levels of KLF4 mRNA and proteins in LNCaP-shKLF4 cells were lower than those in LNCaPcon cells (P<0.01, P<0.05). The expression levels of E-cadherin (E-cad) mRNA in PC3- shKLF4 and LNCaP-shKLF4 cells were higher than those in PC3-con and LNCaP-con cells, respectively (both P<0.01). The expression levels of N-cadherin (N-cad), Zinc finger E-box-binding homeobox 1 (Zeb1), Snail1, vimentin (Vim) and matrix metallopeptidase 1 (MMP1) mRNAs in PC3-shKLF4 and LNCaP-shKLF4 cells were lower than those in PC3-con and LNCaP-con cells, respectively (all P<0.05). The expression levels of E-cad protein in PC3-shKLF4 and LNCaP-shKLF4 cells were higher than those in PC3-con and LNCaP-con cells, respectively (both P<0.05). The expression levels of N-cad, Zeb1, Snail1, Vim and MMP1 mRNAs in PC3-shKLF4 and LNCaP-shKLF4 cells were lower than those in PC3-con and LNCaP-con cells, respectively (all P<0.05). The abilities of migration and invasion of PC3-shKLF4 and LNCaP-shKLF4 cells were weaker than those of PC3-con and LNCaP-con cells, respectively (P<0.01, P<0.05). Conclusion: KLF 4 knockdown in prostate cancer cells can activate the expression of epithelium-associated genes and inhibit the expressions of mesenchymal-associated genes, resulting in the inhibition of cell migration and invasion of prostate cancer cells in vitro.