Background: Previous study has reported that loss of epithelial androgen receptor (AR) may promote tumor progression and cause TRAMP mouse model die earlier. The detail mechanisms, however, remain unclear. Methods: Immunohistochemistry assay, Western blot and real-time PCR were used to detect the expression of epithelial and mesenchymal markers. RNA extraction, RT-PCR, quantitative RT-PCR, BrdU incorporation assays, flow cytometry and other experimental technics were also used in present work. Results: Decreased expression of epithelial markers (Cytokeratin 8, NKX3.1 and E-cadherin) and increased expression of mesenchymal markers (α-SMA, Vimentin, and N-cadherin) in were found in AR knockout TRAMP tumors. Further investigation indicated that AR signal deprivation is associated with cell morphology transition, high cell mobility, high cell invasion rate and resistance to anoikis in TRAMP prostate tumor cells. Together, these findings implied knockout AR in TRAMP prostate tumor may lead to EMT, which may result in earlier metastasis, and then cause TRAMP mice die earlier. TGF-β1 is responsible for EMT in AR knockout TRAMP tumor cells. Conclusions: In conclusion, ADT therapy induced hormone refractory prostate cancer may gain the ability of metastasis through cell's EMT which is a phase of poor differentiation. Anti-EMT drugs should be developed to battle the tumor metastasis induced by ADT therapy.